vendor/rails/railties/doc/guides/html/getting_started_with_rails.html

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 183                 <div id="logo">
 184                         <a href="index.html" title="Ruby on Rails"><img src="images/rails_logo_remix.gif" alt="Rails" height="140" width="110" /></a>
 185                 </div>
 186
 187                 <h1 id="site_title"><span>Ruby on Rails</span></h1>
 188                 <h2 id="site_title_tagline">Sustainable productivity for web-application development</h2>
 189
 190                 <ul id="navMain">
 191                         <li class="first-child"><a href="http://www.rubyonrails.org/" title="Ruby on Rails" class="ruby_on_rails">Ruby on Rails</a></li>
 192                         <li><a class="manuals" href="index.html" title="Manuals Index">Guides Index</a></li>
 193                 </ul>
 194         </div>
 195
 196         <div id="container">
 197
 198                 <div id="sidebar">
 199                         <h2>Chapters</h2>
 200                         <ol>
 201                                         <li>
 202                                         <a href="#_this_guide_assumes">This Guide Assumes</a>
 203                                         </li>
 204                                         <li>
 205                                         <a href="#_what_is_rails">What is Rails?</a>
 206                                                 <ul>
 207
 208                                                         <li><a href="#_the_mvc_architecture">The MVC Architecture</a></li>
 209
 210                                                         <li><a href="#_the_components_of_rails">The Components of Rails</a></li>
 211
 212                                                         <li><a href="#_rest">REST</a></li>
 213
 214                                                 </ul>
 215                                         </li>
 216                                         <li>
 217                                         <a href="#_creating_a_new_rails_project">Creating a New Rails Project</a>
 218                                                 <ul>
 219
 220                                                         <li><a href="#_installing_rails">Installing Rails</a></li>
 221
 222                                                         <li><a href="#_creating_the_blog_application">Creating the Blog Application</a></li>
 223
 224                                                         <li><a href="#_configuring_a_database">Configuring a Database</a></li>
 225
 226                                                 </ul>
 227                                         </li>
 228                                         <li>
 229                                         <a href="#_hello_rails">Hello, Rails!</a>
 230                                                 <ul>
 231
 232                                                         <li><a href="#_starting_up_the_web_server">Starting up the Web Server</a></li>
 233
 234                                                         <li><a href="#_setting_the_application_home_page">Setting the Application Home Page</a></li>
 235
 236                                                 </ul>
 237                                         </li>
 238                                         <li>
 239                                         <a href="#_getting_up_and_running_quickly_with_scaffolding">Getting Up and Running Quickly With Scaffolding</a>
 240                                         </li>
 241                                         <li>
 242                                         <a href="#_creating_a_resource">Creating a Resource</a>
 243                                                 <ul>
 244
 245                                                         <li><a href="#_running_a_migration">Running a Migration</a></li>
 246
 247                                                         <li><a href="#_adding_a_link">Adding a Link</a></li>
 248
 249                                                         <li><a href="#_working_with_posts_in_the_browser">Working with Posts in the Browser</a></li>
 250
 251                                                         <li><a href="#_the_model">The Model</a></li>
 252
 253                                                         <li><a href="#_adding_some_validation">Adding Some Validation</a></li>
 254
 255                                                         <li><a href="#_using_the_console">Using the Console</a></li>
 256
 257                                                         <li><a href="#_listing_all_posts">Listing All Posts</a></li>
 258
 259                                                         <li><a href="#_customizing_the_layout">Customizing the Layout</a></li>
 260
 261                                                         <li><a href="#_creating_new_posts">Creating New Posts</a></li>
 262
 263                                                         <li><a href="#_showing_an_individual_post">Showing an Individual Post</a></li>
 264
 265                                                         <li><a href="#_editing_posts">Editing Posts</a></li>
 266
 267                                                         <li><a href="#_destroying_a_post">Destroying a Post</a></li>
 268
 269                                                 </ul>
 270                                         </li>
 271                                         <li>
 272                                         <a href="#_drying_up_the_code">DRYing up the Code</a>
 273                                                 <ul>
 274
 275                                                         <li><a href="#_using_partials_to_eliminate_view_duplication">Using Partials to Eliminate View Duplication</a></li>
 276
 277                                                         <li><a href="#_using_filters_to_eliminate_controller_duplication">Using Filters to Eliminate Controller Duplication</a></li>
 278
 279                                                 </ul>
 280                                         </li>
 281                                         <li>
 282                                         <a href="#_adding_a_second_model">Adding a Second Model</a>
 283                                                 <ul>
 284
 285                                                         <li><a href="#_generating_a_model">Generating a Model</a></li>
 286
 287                                                         <li><a href="#_associating_models">Associating Models</a></li>
 288
 289                                                         <li><a href="#_adding_a_route">Adding a Route</a></li>
 290
 291                                                         <li><a href="#_generating_a_controller">Generating a Controller</a></li>
 292
 293                                                         <li><a href="#_building_views">Building Views</a></li>
 294
 295                                                         <li><a href="#_hooking_comments_to_posts">Hooking Comments to Posts</a></li>
 296
 297                                                 </ul>
 298                                         </li>
 299                                         <li>
 300                                         <a href="#_what_s_next">What's Next?</a>
 301                                         </li>
 302                                         <li>
 303                                         <a href="#_changelog">Changelog</a>
 304                                         </li>
 305                         </ol>
 306                 </div>
 307
 308                 <div id="content">
 309                                 <h1>Getting Started With Rails</h1>
 310                         <div id="preamble">
 311 <div class="sectionbody">
 312 <div class="para"><p>This guide covers getting up and running with Ruby on Rails.  After reading it, you should be familiar with:</p></div>
 313 <div class="ilist"><ul>
 314 <li>
 315 <p>
 316 Installing Rails, creating a new Rails application, and connecting your application to a database
 317 </p>
 318 </li>
 319 <li>
 320 <p>
 321 The general layout of a Rails application
 322 </p>
 323 </li>
 324 <li>
 325 <p>
 326 The basic principles of MVC (Model, View Controller) and RESTful design
 327 </p>
 328 </li>
 329 <li>
 330 <p>
 331 How to quickly generate the starting pieces of a Rails application.
 332 </p>
 333 </li>
 334 </ul></div>
 335 </div>
 336 </div>
 337 <h2 id="_this_guide_assumes">1. This Guide Assumes</h2>
 338 <div class="sectionbody">
 339 <div class="para"><p>This guide is designed for beginners who want to get started with a Rails application from scratch. It does not assume that you have any prior experience with Rails. However, to get the most out of it, you need to have some prerequisites installed:</p></div>
 340 <div class="ilist"><ul>
 341 <li>
 342 <p>
 343 The <a href="http://www.ruby-lang.org/en/downloads/">Ruby</a> language
 344 </p>
 345 </li>
 346 <li>
 347 <p>
 348 The <a href="http://rubyforge.org/frs/?group_id=126">RubyGems</a> packaging system
 349 </p>
 350 </li>
 351 <li>
 352 <p>
 353 A working installation of <a href="http://www.sqlite.org/">SQLite</a> (preferred), <a href="http://www.mysql.com/">MySQL</a>, or <a href="http://www.postgresql.org/">PostgreSQL</a>
 354 </p>
 355 </li>
 356 </ul></div>
 357 <div class="para"><p>It is highly recommended that you <strong>familiarize yourself with Ruby before diving into Rails</strong>. You will find it much easier to follow what's going on with a Rails application if you understand basic Ruby syntax. Rails isn't going to magically revolutionize the way you write web applications if you have no experience with the language it uses. There are some good free resources on the net for learning Ruby, including:</p></div>
 358 <div class="ilist"><ul>
 359 <li>
 360 <p>
 361 <a href="http://www.humblelittlerubybook.com/">Mr. Neigborly’s Humble Little Ruby Book</a>
 362 </p>
 363 </li>
 364 <li>
 365 <p>
 366 <a href="http://www.rubycentral.com/book/">Programming Ruby</a>
 367 </p>
 368 </li>
 369 <li>
 370 <p>
 371 <a href="http://poignantguide.net/ruby/">Why's (Poignant) Guide to Ruby</a>
 372 </p>
 373 </li>
 374 </ul></div>
 375 </div>
 376 <h2 id="_what_is_rails">2. What is Rails?</h2>
 377 <div class="sectionbody">
 378 <div class="para"><p>Rails is a web development framework written in the Ruby language. It is designed to make programming web applications easier by making several assumptions about what every developer needs to get started. It allows you to write less code while accomplishing more than many other languages and frameworks. Longtime Rails developers also report that it makes web application development more fun.</p></div>
 379 <div class="para"><p>Rails is <em>opinionated software</em>. That is, it assumes that there is a best way to do things, and it's designed to encourage that best way - and in some cases discourage alternatives. If you learn "The Rails Way" you'll probably discover a tremendous increase in productivity. If you persist in bringing old habits from other languages to your Rails development, and trying to use patterns you learned elsewhere, you may have a less happy experience.</p></div>
 380 <div class="para"><p>The Rails philosophy includes several guiding principles:</p></div>
 381 <div class="ilist"><ul>
 382 <li>
 383 <p>
 384 DRY - "Don't Repeat Yourself" - suggests that writing the same code over and over again is a bad thing.
 385 </p>
 386 </li>
 387 <li>
 388 <p>
 389 Convention Over Configuration - means that Rails makes assumptions about what you want to do and how you're going to do it, rather than letting you tweak every little thing through endless configuration files.
 390 </p>
 391 </li>
 392 <li>
 393 <p>
 394 REST is the best pattern for web applications - organizing your application around resources and standard HTTP verbs is the fastest way to go.
 395 </p>
 396 </li>
 397 </ul></div>
 398 <h3 id="_the_mvc_architecture">2.1. The MVC Architecture</h3>
 399 <div class="para"><p>Rails is organized around the Model, View, Controller architecture, usually just called MVC. MVC benefits include:</p></div>
 400 <div class="ilist"><ul>
 401 <li>
 402 <p>
 403 Isolation of business logic from the user interface
 404 </p>
 405 </li>
 406 <li>
 407 <p>
 408 Ease of keeping code DRY
 409 </p>
 410 </li>
 411 <li>
 412 <p>
 413 Making it clear where different types of code belong for easier maintenance
 414 </p>
 415 </li>
 416 </ul></div>
 417 <h4 id="_models">2.1.1. Models</h4>
 418 <div class="para"><p>A model represents the information (data) of the application and the rules to manipulate that data. In the case of Rails, models are primarily used for managing the rules of interaction with a corresponding database table. In most cases, one table in your database will correspond to one model in your application. The bulk of your application's business logic will be concentrated in the models.</p></div>
 419 <h4 id="_views">2.1.2. Views</h4>
 420 <div class="para"><p>Views represent the user interface of your application. In Rails, views are often HTML files with embedded Ruby code that performs tasks related solely to the presentation of the data. Views handle the job of providing data to the web browser or other tool that is used to make requests from your application.</p></div>
 421 <h4 id="_controllers">2.1.3. Controllers</h4>
 422 <div class="para"><p>Controllers provide the "glue" between models and views. In Rails, controllers are responsible for processing the incoming requests from the web browser, interrogating the models for data, and passing that data on to the views for presentation.</p></div>
 423 <h3 id="_the_components_of_rails">2.2. The Components of Rails</h3>
 424 <div class="para"><p>Rails provides a full stack of components for creating web applications, including:</p></div>
 425 <div class="ilist"><ul>
 426 <li>
 427 <p>
 428 Action Controller
 429 </p>
 430 </li>
 431 <li>
 432 <p>
 433 Action View
 434 </p>
 435 </li>
 436 <li>
 437 <p>
 438 Active Record
 439 </p>
 440 </li>
 441 <li>
 442 <p>
 443 Action Mailer
 444 </p>
 445 </li>
 446 <li>
 447 <p>
 448 Active Resource
 449 </p>
 450 </li>
 451 <li>
 452 <p>
 453 Railties
 454 </p>
 455 </li>
 456 <li>
 457 <p>
 458 Active Support
 459 </p>
 460 </li>
 461 </ul></div>
 462 <h4 id="_action_controller">2.2.1. Action Controller</h4>
 463 <div class="para"><p>Action Controller is the component that manages the controllers in a Rails application. The Action Controller framework processes incoming requests to a Rails application, extracts parameters, and dispatches them to the intended action. Services provided by Action Controller include session management, template rendering, and redirect management.</p></div>
 464 <h4 id="_action_view">2.2.2. Action View</h4>
 465 <div class="para"><p>Action View manages the views of your Rails application. It can create both HTML and XML output by default. Action View manages rendering templates, including nested and partial templates, and includes built-in AJAX support.</p></div>
 466 <h4 id="_active_record">2.2.3. Active Record</h4>
 467 <div class="para"><p>Active Record is the base for the models in a Rails application. It provides database independence, basic CRUD functionality, advanced finding capabilities, and the ability to relate models to one another, among other services.</p></div>
 468 <h4 id="_action_mailer">2.2.4. Action Mailer</h4>
 469 <div class="para"><p>Action Mailer is a framework for building e-mail services. You can use Action Mailer to send emails based on flexible templates, or to receive and process incoming email.</p></div>
 470 <h4 id="_active_resource">2.2.5. Active Resource</h4>
 471 <div class="para"><p>Active Resource provides a framework for managing the connection between business objects an RESTful web services. It implements a way to map web-based resources to local objects with CRUD semantics.</p></div>
 472 <h4 id="_railties">2.2.6. Railties</h4>
 473 <div class="para"><p>Railties is the core Rails code that builds new Rails applications and glues the various frameworks together in any Rails application.</p></div>
 474 <h4 id="_active_support">2.2.7. Active Support</h4>
 475 <div class="para"><p>Active Support is an extensive collection of utility classes and standard Ruby library extensions that are used in the Rails, both by the core code and by your applications.</p></div>
 476 <h3 id="_rest">2.3. REST</h3>
 477 <div class="para"><p>The foundation of the RESTful architecture is generally considered to be Roy Fielding's doctoral thesis, <a href="http://www.ics.uci.edu/~fielding/pubs/dissertation/top.htm">Architectural Styles and the Design of Network-based Software Architectures</a>. Fortunately, you need not read this entire document to understand how REST works in Rails. REST, an acronym for Representational State Transfer, boils down to two main principles for our purposes:</p></div>
 478 <div class="ilist"><ul>
 479 <li>
 480 <p>
 481 Using resource identifiers (which, for the purposes of discussion, you can think of as URLs) to represent resources
 482 </p>
 483 </li>
 484 <li>
 485 <p>
 486 Transferring representations of the state of that resource between system components.
 487 </p>
 488 </li>
 489 </ul></div>
 490 <div class="para"><p>For example, to a Rails application a request such as this:</p></div>
 491 <div class="para"><p><tt>DELETE /photos/17</tt></p></div>
 492 <div class="para"><p>would be understood to refer to a photo resource with the ID of 17, and to indicate a desired action - deleting that resource. REST is a natural style for the architecture of web applications, and Rails makes it even more natural by using conventions to shield you from some of the RESTful complexities.</p></div>
 493 <div class="para"><p>If you’d like more details on REST as an architectural style, these resources are more approachable than Fielding’s thesis:</p></div>
 494 <div class="ilist"><ul>
 495 <li>
 496 <p>
 497 <a href="http://www.infoq.com/articles/rest-introduction">A Brief Introduction to REST</a> by Stefan Tilkov
 498 </p>
 499 </li>
 500 <li>
 501 <p>
 502 <a href="http://bitworking.org/news/373/An-Introduction-to-REST">An Introduction to REST</a> (video tutorial) by Joe Gregorio
 503 </p>
 504 </li>
 505 <li>
 506 <p>
 507 <a href="http://en.wikipedia.org/wiki/Representational_State_Transfer">Representational State Transfer</a> article in Wikipedia
 508 </p>
 509 </li>
 510 </ul></div>
 511 </div>
 512 <h2 id="_creating_a_new_rails_project">3. Creating a New Rails Project</h2>
 513 <div class="sectionbody">
 514 <div class="para"><p>If you follow this guide, you'll create a Rails project called <tt>blog</tt>, a (very) simple weblog. Before you can start building the application, you need to make sure that you have Rails itself installed.</p></div>
 515 <h3 id="_installing_rails">3.1. Installing Rails</h3>
 516 <div class="para"><p>In most cases, the easiest way to install Rails is to take advantage of RubyGems:</p></div>
 517 <div class="listingblock">
 518 <div class="content"><!-- Generator: GNU source-highlight 2.9
 519 by Lorenzo Bettini
 520 http://www.lorenzobettini.it
 521 http://www.gnu.org/software/src-highlite -->
 522 <pre><tt>$ gem install rails
 523 </tt></pre></div></div>
 524 <div class="admonitionblock">
 525 <table><tr>
 526 <td class="icon">
 527 <img src="./images/icons/note.png" alt="Note" />
 528 </td>
 529 <td class="content">There are some special circumstances in which you might want to use an alternate installation strategy:</td>
 530 </tr></table>
 531 </div>
 532 <div class="ilist"><ul>
 533 <li>
 534 <p>
 535 If you're working on Windows, you may find it easier to install <a href="http://instantrails.rubyforge.org/wiki/wiki.pl">Instant Rails</a>. Be aware, though, that Instant Rails releases tend to lag seriously behind the actual Rails version. Also, you will find that Rails development on Windows is overall less pleasant than on other operating systems. If at all possible, we suggest that you install a Linux virtual machine and use that for Rails development, instead of using Windows.
 536 </p>
 537 </li>
 538 <li>
 539 <p>
 540 If you want to keep up with cutting-edge changes to Rails, you'll want to clone the <a href="http://github.com/rails/rails/tree/master">Rails source code</a> from github. This is not recommended as an option for beginners, though.
 541 </p>
 542 </li>
 543 </ul></div>
 544 <h3 id="_creating_the_blog_application">3.2. Creating the Blog Application</h3>
 545 <div class="para"><p>Open a terminal, navigate to a folder where you have rights to create files, and type:</p></div>
 546 <div class="listingblock">
 547 <div class="content"><!-- Generator: GNU source-highlight 2.9
 548 by Lorenzo Bettini
 549 http://www.lorenzobettini.it
 550 http://www.gnu.org/software/src-highlite -->
 551 <pre><tt>$ rails blog
 552 </tt></pre></div></div>
 553 <div class="para"><p>This will create a Rails application that uses a SQLite database for data storage. If you prefer to use MySQL, run this command instead:</p></div>
 554 <div class="listingblock">
 555 <div class="content"><!-- Generator: GNU source-highlight 2.9
 556 by Lorenzo Bettini
 557 http://www.lorenzobettini.it
 558 http://www.gnu.org/software/src-highlite -->
 559 <pre><tt>$ rails blog -d mysql
 560 </tt></pre></div></div>
 561 <div class="para"><p>And if you're using PostgreSQL for data storage, run this command:</p></div>
 562 <div class="listingblock">
 563 <div class="content"><!-- Generator: GNU source-highlight 2.9
 564 by Lorenzo Bettini
 565 http://www.lorenzobettini.it
 566 http://www.gnu.org/software/src-highlite -->
 567 <pre><tt>$ rails blog -d postgresql
 568 </tt></pre></div></div>
 569 <div class="para"><p>In any case, Rails will create a folder in your working directory called <tt>blog</tt>. Open up that folder and explore its contents. Most of the work in this tutorial will happen in the <tt>app/</tt> folder, but here's a basic rundown on the function of each folder that Rails creates in a new application by default:</p></div>
 570 <div class="tableblock">
 571 <table rules="all"
 572 frame="hsides"
 573 cellspacing="0" cellpadding="4">
 574 <col width="137" />
 575 <col width="1440" />
 576 <thead>
 577   <tr>
 578     <th align="left">
 579     File/Folder
 580     </th>
 581     <th align="left">
 582     Purpose
 583     </th>
 584   </tr>
 585 </thead>
 586 <tbody valign="top">
 587   <tr>
 588     <td align="left">
 589     <tt>README</tt>
 590     </td>
 591     <td align="left">
 592     This is a brief instruction manual for your application. Use it to tell others what your application does, how to set it up, and so on.
 593     </td>
 594   </tr>
 595   <tr>
 596     <td align="left">
 597     <tt>Rakefile</tt>
 598     </td>
 599     <td align="left">
 600     This file contains batch jobs that can be run from the terminal.
 601     </td>
 602   </tr>
 603   <tr>
 604     <td align="left">
 605     <tt>app/</tt>
 606     </td>
 607     <td align="left">
 608     Contains the controllers, models, and views for your application. You'll focus on this folder for the remainder of this guide.
 609     </td>
 610   </tr>
 611   <tr>
 612     <td align="left">
 613     <tt>config/</tt>
 614     </td>
 615     <td align="left">
 616     Configure your application's runtime rules, routes, database, and more.
 617     </td>
 618   </tr>
 619   <tr>
 620     <td align="left">
 621     <tt>db/</tt>
 622     </td>
 623     <td align="left">
 624     Shows your current database schema, as well as the database migrations. You'll learn about migrations shortly.
 625     </td>
 626   </tr>
 627   <tr>
 628     <td align="left">
 629     <tt>doc/</tt>
 630     </td>
 631     <td align="left">
 632     In-depth documentation for your application.
 633     </td>
 634   </tr>
 635   <tr>
 636     <td align="left">
 637     <tt>lib/</tt>
 638     </td>
 639     <td align="left">
 640     Extended modules for your application (not covered in this guide).
 641     </td>
 642   </tr>
 643   <tr>
 644     <td align="left">
 645     <tt>log/</tt>
 646     </td>
 647     <td align="left">
 648     Application log files.
 649     </td>
 650   </tr>
 651   <tr>
 652     <td align="left">
 653     <tt>public/</tt>
 654     </td>
 655     <td align="left">
 656     The only folder seen to the world as-is.  This is where your images, javascript, stylesheets (CSS), and other static files go.
 657     </td>
 658   </tr>
 659   <tr>
 660     <td align="left">
 661     <tt>script/</tt>
 662     </td>
 663     <td align="left">
 664     Scripts provided by Rails to do recurring tasks, such as benchmarking, plugin installation, and starting the console or the web server.
 665     </td>
 666   </tr>
 667   <tr>
 668     <td align="left">
 669     <tt>test/</tt>
 670     </td>
 671     <td align="left">
 672     Unit tests, fixtures, and other test apparatus. These are covered in <a href="../testing_rails_applications.html">Testing Rails Applications</a>
 673     </td>
 674   </tr>
 675   <tr>
 676     <td align="left">
 677     <tt>tmp/</tt>
 678     </td>
 679     <td align="left">
 680     Temporary files
 681     </td>
 682   </tr>
 683   <tr>
 684     <td align="left">
 685     <tt>vendor/</tt>
 686     </td>
 687     <td align="left">
 688     A place for third-party code. In a typical Rails application, this includes Ruby Gems, the Rails source code (if you install it into your project) and plugins containing additional prepackaged functionality.
 689     </td>
 690   </tr>
 691 </tbody>
 692 </table>
 693 </div>
 694 <h3 id="_configuring_a_database">3.3. Configuring a Database</h3>
 695 <div class="para"><p>Just about every Rails application will interact with a database. The database to use is specified in a configuration file, <tt>config/database.yml</tt>.
 696 If you open this file in a new Rails application, you'll see a default database configuration using SQLite. The file contains sections for three different environments in which Rails can run by default:</p></div>
 697 <div class="ilist"><ul>
 698 <li>
 699 <p>
 700 The <tt>development</tt> environment is used on your development computer as you interact manually with the application
 701 </p>
 702 </li>
 703 <li>
 704 <p>
 705 The <tt>test</tt> environment is used to run automated tests
 706 </p>
 707 </li>
 708 <li>
 709 <p>
 710 The <tt>production</tt> environment is used when you deploy your application for the world to use.
 711 </p>
 712 </li>
 713 </ul></div>
 714 <h4 id="_configuring_a_sqlite_database">3.3.1. Configuring a SQLite Database</h4>
 715 <div class="para"><p>Rails comes with built-in support for <a href="http://www.sqlite.org/">SQLite</a>, which is a lightweight serverless database application. While a busy production environment may overload SQLite, it works well for development and testing. Rails defaults to using a SQLite database when creating a new project, but you can always change it later.</p></div>
 716 <div class="para"><p>Here's the section of the default configuration file with connection information for the development environment:</p></div>
 717 <div class="listingblock">
 718 <div class="content"><!-- Generator: GNU source-highlight 2.9
 719 by Lorenzo Bettini
 720 http://www.lorenzobettini.it
 721 http://www.gnu.org/software/src-highlite -->
 722 <pre><tt>development<span style="color: #990000">:</span>
 723   adapter<span style="color: #990000">:</span> sqlite3
 724   database<span style="color: #990000">:</span> db<span style="color: #990000">/</span>development<span style="color: #990000">.</span>sqlite3
 725   timeout<span style="color: #990000">:</span> <span style="color: #993399">5000</span>
 726 </tt></pre></div></div>
 727 <div class="para"><p>If you don't have any database set up, SQLite is the easiest to get installed. If you're on OS X 10.5 or greater on a Mac, you already have it. Otherwise, you can install it using RubyGems:</p></div>
 728 <div class="para"><p>If you're not running OS X 10.5 or greater, you'll need to install the SQLite gem.  Similar to installing Rails you just need to run:</p></div>
 729 <div class="listingblock">
 730 <div class="content"><!-- Generator: GNU source-highlight 2.9
 731 by Lorenzo Bettini
 732 http://www.lorenzobettini.it
 733 http://www.gnu.org/software/src-highlite -->
 734 <pre><tt>$ gem install sqlite3-ruby
 735 </tt></pre></div></div>
 736 <h4 id="_configuring_a_mysql_database">3.3.2. Configuring a MySQL Database</h4>
 737 <div class="para"><p>If you choose to use MySQL, your <tt>config/database.yml</tt> will look a little different. Here's the development section:</p></div>
 738 <div class="listingblock">
 739 <div class="content"><!-- Generator: GNU source-highlight 2.9
 740 by Lorenzo Bettini
 741 http://www.lorenzobettini.it
 742 http://www.gnu.org/software/src-highlite -->
 743 <pre><tt>development<span style="color: #990000">:</span>
 744   adapter<span style="color: #990000">:</span> mysql
 745   encoding<span style="color: #990000">:</span> utf8
 746   database<span style="color: #990000">:</span> blog_development
 747   username<span style="color: #990000">:</span> root
 748   password<span style="color: #990000">:</span>
 749   socket<span style="color: #990000">:</span> <span style="color: #FF6600">/tmp/</span>mysql<span style="color: #990000">.</span>sock
 750 </tt></pre></div></div>
 751 <div class="para"><p>If your development computer's MySQL installation includes a root user with an empty password, this configuration should work for you. Otherwise, change the username and password in the <tt>development</tt> section as appropriate.</p></div>
 752 <h4 id="_configuring_a_postgresql_database">3.3.3. Configuring a PostgreSQL Database</h4>
 753 <div class="para"><p>If you choose to use PostgreSQL, your <tt>config/database.yml</tt> will be customized to use PostgreSQL databases:</p></div>
 754 <div class="listingblock">
 755 <div class="content"><!-- Generator: GNU source-highlight 2.9
 756 by Lorenzo Bettini
 757 http://www.lorenzobettini.it
 758 http://www.gnu.org/software/src-highlite -->
 759 <pre><tt>development<span style="color: #990000">:</span>
 760   adapter<span style="color: #990000">:</span> postgresql
 761   encoding<span style="color: #990000">:</span> unicode
 762   database<span style="color: #990000">:</span> blog_development
 763   username<span style="color: #990000">:</span> blog
 764   password<span style="color: #990000">:</span>
 765 </tt></pre></div></div>
 766 <div class="para"><p>Change the username and password in the <tt>development</tt> section as appropriate.</p></div>
 767 </div>
 768 <h2 id="_hello_rails">4. Hello, Rails!</h2>
 769 <div class="sectionbody">
 770 <div class="para"><p>One of the traditional places to start with a new language is by getting some text up on screen quickly. To do that in Rails, you need to create at minimum a controller and a view. Fortunately, you can do that in a single command. Enter this command in your terminal:</p></div>
 771 <div class="listingblock">
 772 <div class="content"><!-- Generator: GNU source-highlight 2.9
 773 by Lorenzo Bettini
 774 http://www.lorenzobettini.it
 775 http://www.gnu.org/software/src-highlite -->
 776 <pre><tt>$ script/generate controller home index
 777 </tt></pre></div></div>
 778 <div class="admonitionblock">
 779 <table><tr>
 780 <td class="icon">
 781 <img src="./images/icons/tip.png" alt="Tip" />
 782 </td>
 783 <td class="content">If you're on Windows, or your Ruby is set up in some non-standard fashion, you may need to explicitly pass Rails <tt>script</tt> commands to Ruby: <tt>ruby script/generate controller home index</tt>.</td>
 784 </tr></table>
 785 </div>
 786 <div class="para"><p>Rails will create several files for you, including <tt>app/views/home/index.html.erb</tt>. This is the template that will be used to display the results of the <tt>index</tt> action (method) in the <tt>home</tt> controller. Open this file in your text editor and edit it to contain a single line of code:</p></div>
 787 <div class="listingblock">
 788 <div class="content"><!-- Generator: GNU source-highlight 2.9
 789 by Lorenzo Bettini
 790 http://www.lorenzobettini.it
 791 http://www.gnu.org/software/src-highlite -->
 792 <pre><tt><span style="font-weight: bold"><span style="color: #0000FF">&lt;h1&gt;</span></span>Hello, Rails!<span style="font-weight: bold"><span style="color: #0000FF">&lt;/h1&gt;</span></span>
 793 </tt></pre></div></div>
 794 <h3 id="_starting_up_the_web_server">4.1. Starting up the Web Server</h3>
 795 <div class="para"><p>You actually have a functional Rails application already - after running only two commands! To see it, you need to start a web server on your development machine. You can do this by running another command:</p></div>
 796 <div class="listingblock">
 797 <div class="content"><!-- Generator: GNU source-highlight 2.9
 798 by Lorenzo Bettini
 799 http://www.lorenzobettini.it
 800 http://www.gnu.org/software/src-highlite -->
 801 <pre><tt>$ script/server
 802 </tt></pre></div></div>
 803 <div class="para"><p>This will fire up the lightweight Webrick web server by default. To see your application in action, open a browser window and navigate to <tt>http://localhost:3000</tt>. You should see Rails' default information page:</p></div>
 804 <div class="para"><p><span class="image">
 805 <img src="images/rails_welcome.png" alt="Welcome Aboard screenshot" title="Welcome Aboard screenshot" />
 806 </span></p></div>
 807 <div class="admonitionblock">
 808 <table><tr>
 809 <td class="icon">
 810 <img src="./images/icons/tip.png" alt="Tip" />
 811 </td>
 812 <td class="content">To stop the web server, hit Ctrl+C in the terminal window where it's running. In development mode, Rails does not generally require you to stop the server; changes you make in files will be automatically picked up by the server.</td>
 813 </tr></table>
 814 </div>
 815 <div class="para"><p>The "Welcome Aboard" page is the smoke test for a new Rails application: it makes sure that you have your software configured correctly enough to serve a page. To view the page you just created, navigate to <tt>http://localhost:3000/home/index</tt>.</p></div>
 816 <h3 id="_setting_the_application_home_page">4.2. Setting the Application Home Page</h3>
 817 <div class="para"><p>You'd probably like to replace the "Welcome Aboard" page with your own application's home page. The first step to doing this is to delete the default page from your application:</p></div>
 818 <div class="listingblock">
 819 <div class="content"><!-- Generator: GNU source-highlight 2.9
 820 by Lorenzo Bettini
 821 http://www.lorenzobettini.it
 822 http://www.gnu.org/software/src-highlite -->
 823 <pre><tt>$ rm public/index<span style="color: #990000">.</span>html
 824 </tt></pre></div></div>
 825 <div class="para"><p>Now, you have to tell Rails where your actual home page is located. Open the file <tt>config/routes.rb</tt> in your editor. This is your application's, <em>routing file</em>, which holds entries in a special DSL (domain-specific language) that tells Rails how to connect incoming requests to controllers and actions. At the bottom of the file you'll see the <em>default routes</em>:</p></div>
 826 <div class="listingblock">
 827 <div class="content"><!-- Generator: GNU source-highlight 2.9
 828 by Lorenzo Bettini
 829 http://www.lorenzobettini.it
 830 http://www.gnu.org/software/src-highlite -->
 831 <pre><tt>map<span style="color: #990000">.</span>connect <span style="color: #FF0000">':controller/:action/:id'</span>
 832 map<span style="color: #990000">.</span>connect <span style="color: #FF0000">':controller/:action/:id.:format'</span>
 833 </tt></pre></div></div>
 834 <div class="para"><p>The default routes handle simple requests such as <tt>/home/index</tt>: Rails translates that into a call to the <tt>index</tt> action in the <tt>home</tt> controller. As another example, <tt>/posts/edit/1</tt> would run the <tt>edit</tt> action in the <tt>posts</tt> controller with an <tt>id</tt> of 1.</p></div>
 835 <div class="para"><p>To hook up your home page, you need to add another line to the routing file, above the default routes:</p></div>
 836 <div class="listingblock">
 837 <div class="content"><!-- Generator: GNU source-highlight 2.9
 838 by Lorenzo Bettini
 839 http://www.lorenzobettini.it
 840 http://www.gnu.org/software/src-highlite -->
 841 <pre><tt>map<span style="color: #990000">.</span>root <span style="color: #990000">:</span>controller <span style="color: #990000">=&gt;</span> <span style="color: #FF0000">"home"</span>
 842 </tt></pre></div></div>
 843 <div class="para"><p>This line illustrates one tiny bit of the "convention over configuration" approach: if you don't specify an action, Rails assumes the <tt>index</tt> action.</p></div>
 844 <div class="para"><p>Now if you navigate to <tt>http://localhost:3000</tt> in your browser, you'll see the <tt>home/index</tt> view.</p></div>
 845 <div class="admonitionblock">
 846 <table><tr>
 847 <td class="icon">
 848 <img src="./images/icons/note.png" alt="Note" />
 849 </td>
 850 <td class="content">For more information about routing, refer to <a href="../routing_outside_in.html">Rails Routing from the Outside In</a>.</td>
 851 </tr></table>
 852 </div>
 853 </div>
 854 <h2 id="_getting_up_and_running_quickly_with_scaffolding">5. Getting Up and Running Quickly With Scaffolding</h2>
 855 <div class="sectionbody">
 856 <div class="para"><p>Rails <em>scaffolding</em> is a quick way to generate some of the major pieces of an application. If you want to create the models, views, and controllers for a new resource in a single operation, scaffolding is the tool for the job.</p></div>
 857 </div>
 858 <h2 id="_creating_a_resource">6. Creating a Resource</h2>
 859 <div class="sectionbody">
 860 <div class="para"><p>In the case of the blog application, you can start by generating a scaffolded Post resource: this will represent a single blog posting. To do this, enter this command in your terminal:</p></div>
 861 <div class="listingblock">
 862 <div class="content"><!-- Generator: GNU source-highlight 2.9
 863 by Lorenzo Bettini
 864 http://www.lorenzobettini.it
 865 http://www.gnu.org/software/src-highlite -->
 866 <pre><tt>$ script/generate scaffold Post name<span style="color: #990000">:</span>string title<span style="color: #990000">:</span>string content<span style="color: #990000">:</span>text
 867 </tt></pre></div></div>
 868 <div class="admonitionblock">
 869 <table><tr>
 870 <td class="icon">
 871 <img src="./images/icons/note.png" alt="Note" />
 872 </td>
 873 <td class="content">While scaffolding will get you up and running quickly, the "one size fits all" code that it generates is unlikely to be a perfect fit for your application. In most cases, you'll need to customize the generated code. Many experienced Rails developers avoid scaffolding entirely, preferring to write all or most of their source code from scratch.</td>
 874 </tr></table>
 875 </div>
 876 <div class="para"><p>The scaffold generator will build 13 files in your application, along with some folders, and edit one more. Here's a quick overview of what it creates:</p></div>
 877 <div class="tableblock">
 878 <table rules="all"
 879 frame="hsides"
 880 cellspacing="0" cellpadding="4">
 881 <col width="525" />
 882 <col width="1062" />
 883 <thead>
 884   <tr>
 885     <th align="left">
 886     File
 887     </th>
 888     <th align="left">
 889     Purpose
 890     </th>
 891   </tr>
 892 </thead>
 893 <tbody valign="top">
 894   <tr>
 895     <td align="left">
 896     app/models/post.rb
 897     </td>
 898     <td align="left">
 899     The Post model
 900     </td>
 901   </tr>
 902   <tr>
 903     <td align="left">
 904     db/migrate/20081013124235_create_posts.rb
 905     </td>
 906     <td align="left">
 907     Migration to create the posts table in your database (your name will include a different timestamp)
 908     </td>
 909   </tr>
 910   <tr>
 911     <td align="left">
 912     app/views/posts/index.html.erb
 913     </td>
 914     <td align="left">
 915     A view to display an index of all posts
 916     </td>
 917   </tr>
 918   <tr>
 919     <td align="left">
 920     app/views/posts/show.html.erb
 921     </td>
 922     <td align="left">
 923     A view to display a single post
 924     </td>
 925   </tr>
 926   <tr>
 927     <td align="left">
 928     app/views/posts/new.html.erb
 929     </td>
 930     <td align="left">
 931     A view to create a new post
 932     </td>
 933   </tr>
 934   <tr>
 935     <td align="left">
 936     app/views/posts/edit.html.erb
 937     </td>
 938     <td align="left">
 939     A view to edit an existing post
 940     </td>
 941   </tr>
 942   <tr>
 943     <td align="left">
 944     app/views/layouts/posts.html.erb
 945     </td>
 946     <td align="left">
 947     A view to control the overall look and feel of the other posts views
 948     </td>
 949   </tr>
 950   <tr>
 951     <td align="left">
 952     public/stylesheets/scaffold.css
 953     </td>
 954     <td align="left">
 955     Cascading style sheet to make the scaffolded views look better
 956     </td>
 957   </tr>
 958   <tr>
 959     <td align="left">
 960     app/controllers/posts_controller.rb
 961     </td>
 962     <td align="left">
 963     The Posts controller
 964     </td>
 965   </tr>
 966   <tr>
 967     <td align="left">
 968     test/functional/posts_controller_test.rb
 969     </td>
 970     <td align="left">
 971     Functional testing harness for the posts controller
 972     </td>
 973   </tr>
 974   <tr>
 975     <td align="left">
 976     app/helpers/posts_helper.rb
 977     </td>
 978     <td align="left">
 979     Helper functions to be used from the posts views
 980     </td>
 981   </tr>
 982   <tr>
 983     <td align="left">
 984     config/routes.rb
 985     </td>
 986     <td align="left">
 987     Edited to include routing information for posts
 988     </td>
 989   </tr>
 990   <tr>
 991     <td align="left">
 992     test/fixtures/posts.yml
 993     </td>
 994     <td align="left">
 995     Dummy posts for use in testing
 996     </td>
 997   </tr>
 998   <tr>
 999     <td align="left">
1000     test/unit/post_test.rb
1001     </td>
1002     <td align="left">
1003     Unit testing harness for the posts model
1004     </td>
1005   </tr>
1006 </tbody>
1007 </table>
1008 </div>
1009 <h3 id="_running_a_migration">6.1. Running a Migration</h3>
1010 <div class="para"><p>One of the products of the <tt>script/generate scaffold</tt> command is a <em>database migration</em>. Migrations are Ruby classes that are designed to make it simple to create and modify database tables. Rails uses rake commands to run migrations, and it's possible to undo a migration after it's been applied to your database. Migration filenames include a timestamp to ensure that they're processed in the order that they were created.</p></div>
1011 <div class="para"><p>If you look in the <tt>db/migrate/20081013124235_create_posts.rb</tt> file (remember, yours will have a slightly different name), here's what you'll find:</p></div>
1012 <div class="listingblock">
1013 <div class="content"><!-- Generator: GNU source-highlight 2.9
1014 by Lorenzo Bettini
1015 http://www.lorenzobettini.it
1016 http://www.gnu.org/software/src-highlite -->
1017 <pre><tt><span style="font-weight: bold"><span style="color: #0000FF">class</span></span> CreatePosts <span style="color: #990000">&lt;</span> ActiveRecord<span style="color: #990000">::</span>Migration
1018   <span style="font-weight: bold"><span style="color: #0000FF">def</span></span> <span style="font-weight: bold"><span style="color: #0000FF">self</span></span><span style="color: #990000">.</span>up
1019     create_table <span style="color: #990000">:</span>posts <span style="font-weight: bold"><span style="color: #0000FF">do</span></span> <span style="color: #990000">|</span>t<span style="color: #990000">|</span>
1020       t<span style="color: #990000">.</span>string <span style="color: #990000">:</span>name
1021       t<span style="color: #990000">.</span>string <span style="color: #990000">:</span>title
1022       t<span style="color: #990000">.</span>text <span style="color: #990000">:</span>content
1023
1024       t<span style="color: #990000">.</span>timestamps
1025     <span style="font-weight: bold"><span style="color: #0000FF">end</span></span>
1026   <span style="font-weight: bold"><span style="color: #0000FF">end</span></span>
1027
1028   <span style="font-weight: bold"><span style="color: #0000FF">def</span></span> <span style="font-weight: bold"><span style="color: #0000FF">self</span></span><span style="color: #990000">.</span>down
1029     drop_table <span style="color: #990000">:</span>posts
1030   <span style="font-weight: bold"><span style="color: #0000FF">end</span></span>
1031 <span style="font-weight: bold"><span style="color: #0000FF">end</span></span>
1032 </tt></pre></div></div>
1033 <div class="para"><p>If you were to translate that into words, it says something like: when this migration is run, create a table named <tt>posts</tt> with two string columns (<tt>name</tt> and <tt>title</tt>) and a text column (<tt>content</tt>), and generate timestamp fields to track record creation and updating. You can learn the detailed syntax for migrations in the <a href="../migrations.html">Rails Database Migrations</a> guide.</p></div>
1034 <div class="para"><p>At this point, you need to do two things: create the database and run the migration. You can use rake commands at the terminal for both of those tasks:</p></div>
1035 <div class="listingblock">
1036 <div class="content"><!-- Generator: GNU source-highlight 2.9
1037 by Lorenzo Bettini
1038 http://www.lorenzobettini.it
1039 http://www.gnu.org/software/src-highlite -->
1040 <pre><tt>$ rake db<span style="color: #990000">:</span>create
1041 $ rake db<span style="color: #990000">:</span>migrate
1042 </tt></pre></div></div>
1043 <div class="admonitionblock">
1044 <table><tr>
1045 <td class="icon">
1046 <img src="./images/icons/note.png" alt="Note" />
1047 </td>
1048 <td class="content">Because you're working in the development environment by default, both of these commands will apply to the database defined in the <tt>development</tt> section of your <tt>config/database.yml</tt> file.</td>
1049 </tr></table>
1050 </div>
1051 <h3 id="_adding_a_link">6.2. Adding a Link</h3>
1052 <div class="para"><p>To hook the posts up to the home page you've already created, you can add a link to the home page. Open <tt>/app/views/home/index.html.erb</tt> and modify it as follows:</p></div>
1053 <div class="listingblock">
1054 <div class="content"><!-- Generator: GNU source-highlight 2.9
1055 by Lorenzo Bettini
1056 http://www.lorenzobettini.it
1057 http://www.gnu.org/software/src-highlite -->
1058 <pre><tt><span style="color: #FF0000">&lt;h1&gt;</span>Hello<span style="color: #990000">,</span> Rails!<span style="color: #FF0000">&lt;/h1&gt;</span>
1059
1060 <span style="color: #FF0000">&lt;%= link_to "My Blog", posts_path %&gt;</span>
1061 </tt></pre></div></div>
1062 <div class="para"><p>The <tt>link_to</tt> method is one of Rails' built-in view helpers. It creates a hyperlink based on text to display and where to go - in this case, to the path for posts.</p></div>
1063 <h3 id="_working_with_posts_in_the_browser">6.3. Working with Posts in the Browser</h3>
1064 <div class="para"><p>Now you're ready to start working with posts. To do that, navigate to <tt>http://localhost:3000</tt> and then click the "My Blog" link:</p></div>
1065 <div class="para"><p><span class="image">
1066 <img src="images/posts_index.png" alt="Posts Index screenshot" title="Posts Index screenshot" />
1067 </span></p></div>
1068 <div class="para"><p>This is the result of Rails rendering the <tt>index</tt> view of your posts. There aren't currently any posts in the database, but if you click the <tt>New Post</tt> link you can create one. After that, you'll find that you can edit posts, look at their details, or destroy them. All of the logic and HTML to handle this was built by the single <tt>script/generate scaffold</tt> command.</p></div>
1069 <div class="admonitionblock">
1070 <table><tr>
1071 <td class="icon">
1072 <img src="./images/icons/tip.png" alt="Tip" />
1073 </td>
1074 <td class="content">In development mode (which is what you're working in by default), Rails reloads your application with every browser request, so there's no need to stop and restart the web server.</td>
1075 </tr></table>
1076 </div>
1077 <div class="para"><p>Congratulations, you're riding the rails! Now it's time to see how it all works.</p></div>
1078 <h3 id="_the_model">6.4. The Model</h3>
1079 <div class="para"><p>The model file, <tt>app/models/post.rb</tt> is about as simple as it can get:</p></div>
1080 <div class="listingblock">
1081 <div class="content"><!-- Generator: GNU source-highlight 2.9
1082 by Lorenzo Bettini
1083 http://www.lorenzobettini.it
1084 http://www.gnu.org/software/src-highlite -->
1085 <pre><tt><span style="font-weight: bold"><span style="color: #0000FF">class</span></span> Post <span style="color: #990000">&lt;</span> ActiveRecord<span style="color: #990000">::</span>Base
1086 <span style="font-weight: bold"><span style="color: #0000FF">end</span></span>
1087 </tt></pre></div></div>
1088 <div class="para"><p>There isn't much to this file - but note that the <tt>Post</tt> class inherits from <tt>ActiveRecord::Base</tt>. Active Record supplies a great deal of functionality to your Rails models for free, including basic database CRUD (Create, Read, Update, Destroy) operations, data validation, as well as sophisticated search support and the ability to relate multiple models to one another.</p></div>
1089 <h3 id="_adding_some_validation">6.5. Adding Some Validation</h3>
1090 <div class="para"><p>Rails includes methods to help you validate the data that you send to models. Open the <tt>app/models/post.rb</tt> file and edit it:</p></div>
1091 <div class="listingblock">
1092 <div class="content"><!-- Generator: GNU source-highlight 2.9
1093 by Lorenzo Bettini
1094 http://www.lorenzobettini.it
1095 http://www.gnu.org/software/src-highlite -->
1096 <pre><tt><span style="font-weight: bold"><span style="color: #0000FF">class</span></span> Post <span style="color: #990000">&lt;</span> ActiveRecord<span style="color: #990000">::</span>Base
1097   validates_presence_of <span style="color: #990000">:</span>name<span style="color: #990000">,</span> <span style="color: #990000">:</span>title
1098   validates_length_of <span style="color: #990000">:</span>title<span style="color: #990000">,</span> <span style="color: #990000">:</span>minimum <span style="color: #990000">=&gt;</span> <span style="color: #993399">5</span>
1099 <span style="font-weight: bold"><span style="color: #0000FF">end</span></span>
1100 </tt></pre></div></div>
1101 <div class="para"><p>These changes will ensure that all posts have a name and a title, and that the title is at least five characters long. Rails can validate a variety of conditions in a model, including the presence or uniqueness of columns, their format, and the existence of associated objects.</p></div>
1102 <h3 id="_using_the_console">6.6. Using the Console</h3>
1103 <div class="para"><p>To see your validations in action, you can use the console. The console is a command-line tool that lets you execute Ruby code in the context of your application:</p></div>
1104 <div class="listingblock">
1105 <div class="content"><!-- Generator: GNU source-highlight 2.9
1106 by Lorenzo Bettini
1107 http://www.lorenzobettini.it
1108 http://www.gnu.org/software/src-highlite -->
1109 <pre><tt>$ script/console
1110 </tt></pre></div></div>
1111 <div class="para"><p>After the console loads, you can use it to work with your application's models:</p></div>
1112 <div class="listingblock">
1113 <div class="content"><!-- Generator: GNU source-highlight 2.9
1114 by Lorenzo Bettini
1115 http://www.lorenzobettini.it
1116 http://www.gnu.org/software/src-highlite -->
1117 <pre><tt><span style="color: #990000">&gt;&gt;</span> p <span style="color: #990000">=</span> Post<span style="color: #990000">.</span>create<span style="color: #990000">(:</span>content <span style="color: #990000">=&gt;</span> <span style="color: #FF0000">"A new post"</span><span style="color: #990000">)</span>
1118 <span style="color: #990000">=&gt;</span> <span style="font-style: italic"><span style="color: #9A1900">#&lt;Post id: nil, name: nil, title: nil, content: "A new post",</span></span>
1119 created_at<span style="color: #990000">:</span> nil<span style="color: #990000">,</span> updated_at<span style="color: #990000">:</span> nil<span style="color: #990000">&gt;</span>
1120 <span style="color: #990000">&gt;&gt;</span> p<span style="color: #990000">.</span>save
1121 <span style="color: #990000">=&gt;</span> <span style="font-weight: bold"><span style="color: #0000FF">false</span></span>
1122 <span style="color: #990000">&gt;&gt;</span> p<span style="color: #990000">.</span>errors
1123 <span style="color: #990000">=&gt;</span> <span style="font-style: italic"><span style="color: #9A1900">#&lt;ActiveRecord::Errors:0x23bcf0c @base=#&lt;Post id: nil, name: nil,</span></span>
1124 title<span style="color: #990000">:</span> nil<span style="color: #990000">,</span> content<span style="color: #990000">:</span> <span style="color: #FF0000">"A new post"</span><span style="color: #990000">,</span> created_at<span style="color: #990000">:</span> nil<span style="color: #990000">,</span> updated_at<span style="color: #990000">:</span> nil<span style="color: #990000">&gt;,</span>
1125 @<span style="color: #009900">errors</span><span style="color: #990000">=</span>{<span style="color: #FF0000">"name"</span><span style="color: #990000">=&gt;[</span><span style="color: #FF0000">"can't be blank"</span><span style="color: #990000">],</span> <span style="color: #FF0000">"title"</span><span style="color: #990000">=&gt;[</span><span style="color: #FF0000">"can't be blank"</span><span style="color: #990000">,</span>
1126 <span style="color: #FF0000">"is too short (minimum is 5 characters)"</span><span style="color: #990000">]</span>}<span style="color: #990000">&gt;</span>
1127 </tt></pre></div></div>
1128 <div class="para"><p>This code shows creating a new <tt>Post</tt> instance, attempting to save it and getting <tt>false</tt> for a return value (indicating that the save failed), and inspecting the <tt>errors</tt> of the post.</p></div>
1129 <div class="admonitionblock">
1130 <table><tr>
1131 <td class="icon">
1132 <img src="./images/icons/tip.png" alt="Tip" />
1133 </td>
1134 <td class="content">Unlike the development web server, the console does not automatically load your code afresh for each line. If you make changes, type <tt>reload!</tt> at the console prompt to load them.</td>
1135 </tr></table>
1136 </div>
1137 <h3 id="_listing_all_posts">6.7. Listing All Posts</h3>
1138 <div class="para"><p>The easiest place to start looking at functionality is with the code that lists all posts. Open the file <tt>app/controllers/posts_controller.rb </tt> and look at the <tt>index</tt> action:</p></div>
1139 <div class="listingblock">
1140 <div class="content"><!-- Generator: GNU source-highlight 2.9
1141 by Lorenzo Bettini
1142 http://www.lorenzobettini.it
1143 http://www.gnu.org/software/src-highlite -->
1144 <pre><tt><span style="font-weight: bold"><span style="color: #0000FF">def</span></span> index
1145   <span style="color: #009900">@posts</span> <span style="color: #990000">=</span> Post<span style="color: #990000">.</span>find<span style="color: #990000">(:</span>all<span style="color: #990000">)</span>
1146
1147   respond_to <span style="font-weight: bold"><span style="color: #0000FF">do</span></span> <span style="color: #990000">|</span>format<span style="color: #990000">|</span>
1148     format<span style="color: #990000">.</span>html <span style="font-style: italic"><span style="color: #9A1900"># index.html.erb</span></span>
1149     format<span style="color: #990000">.</span>xml  <span style="color: #FF0000">{</span> render <span style="color: #990000">:</span>xml <span style="color: #990000">=&gt;</span> <span style="color: #009900">@posts</span> <span style="color: #FF0000">}</span>
1150   <span style="font-weight: bold"><span style="color: #0000FF">end</span></span>
1151 <span style="font-weight: bold"><span style="color: #0000FF">end</span></span>
1152 </tt></pre></div></div>
1153 <div class="para"><p>This code sets the <tt>@posts</tt> instance variable to an array of all posts in the database. <tt>Post.find(:all)</tt> or <tt>Post.all</tt> calls the <tt>Post</tt> model to return all of the posts that are currently in the database, with no limiting conditions.</p></div>
1154 <div class="admonitionblock">
1155 <table><tr>
1156 <td class="icon">
1157 <img src="./images/icons/tip.png" alt="Tip" />
1158 </td>
1159 <td class="content">For more information on finding records with Active Record, see <a href="../finders.html">Active Record Finders</a>.</td>
1160 </tr></table>
1161 </div>
1162 <div class="para"><p>The <tt>respond_to</tt> block handles both HTML and XML calls to this action. If you browse to <tt>http://localhost:3000/posts.xml</tt>, you'll see all of the posts in XML format. The HTML format looks for a view in <tt>app/views/posts/</tt> with a name that corresponds to the action name. Rails makes all of the instance variables from the action available to the view. Here's <tt>app/view/posts/index.html.erb</tt>:</p></div>
1163 <div class="listingblock">
1164 <div class="content"><!-- Generator: GNU source-highlight 2.9
1165 by Lorenzo Bettini
1166 http://www.lorenzobettini.it
1167 http://www.gnu.org/software/src-highlite -->
1168 <pre><tt><span style="color: #FF0000">&lt;h1&gt;</span>Listing posts<span style="color: #FF0000">&lt;/h1&gt;</span>
1169
1170 <span style="color: #FF0000">&lt;table&gt;</span>
1171   <span style="color: #FF0000">&lt;tr&gt;</span>
1172     <span style="color: #FF0000">&lt;th&gt;</span>Name<span style="color: #FF0000">&lt;/th&gt;</span>
1173     <span style="color: #FF0000">&lt;th&gt;</span>Title<span style="color: #FF0000">&lt;/th&gt;</span>
1174     <span style="color: #FF0000">&lt;th&gt;</span>Content<span style="color: #FF0000">&lt;/th&gt;</span>
1175   <span style="color: #FF0000">&lt;/tr&gt;</span>
1176
1177 <span style="color: #FF0000">&lt;% for post in @posts %&gt;</span>
1178   <span style="color: #FF0000">&lt;tr&gt;</span>
1179     <span style="color: #FF0000">&lt;td&gt;&lt;%=h post.name %&gt;&lt;/td&gt;</span>
1180     <span style="color: #FF0000">&lt;td&gt;&lt;%=h post.title %&gt;&lt;/td&gt;</span>
1181     <span style="color: #FF0000">&lt;td&gt;&lt;%=h post.content %&gt;&lt;/td&gt;</span>
1182     <span style="color: #FF0000">&lt;td&gt;&lt;%= link_to 'Show', post %&gt;&lt;/td&gt;</span>
1183     <span style="color: #FF0000">&lt;td&gt;&lt;%= link_to 'Edit', edit_post_path(post) %&gt;&lt;/td&gt;</span>
1184     <span style="color: #FF0000">&lt;td&gt;&lt;%= link_to 'Destroy', post, :confirm =&gt;</span> <span style="color: #FF0000">'Are you sure?'</span><span style="color: #990000">,</span> <span style="color: #990000">:</span>method <span style="color: #990000">=&gt;</span> <span style="color: #990000">:</span>delete <span style="color: #990000">%&gt;</span><span style="color: #FF0000">&lt;/td&gt;</span>
1185   <span style="color: #FF0000">&lt;/tr&gt;</span>
1186 <span style="color: #FF0000">&lt;% end %&gt;</span>
1187 <span style="color: #FF0000">&lt;/table&gt;</span>
1188
1189 <span style="color: #FF0000">&lt;br /&gt;</span>
1190
1191 <span style="color: #FF0000">&lt;%= link_to 'New post', new_post_path %&gt;</span>
1192 </tt></pre></div></div>
1193 <div class="para"><p>This view iterates over the contents of the <tt>@posts</tt> array to display content and links. A few things to note in the view:</p></div>
1194 <div class="ilist"><ul>
1195 <li>
1196 <p>
1197 <tt>h</tt> is a Rails helper method to sanitize displayed data, preventing cross-site scripting attacks
1198 </p>
1199 </li>
1200 <li>
1201 <p>
1202 <tt>link_to</tt> builds a hyperlink to a particular destination
1203 </p>
1204 </li>
1205 <li>
1206 <p>
1207 <tt>edit_post_path</tt> is a helper that Rails provides as part of RESTful routing. You’ll see a variety of these helpers for the different actions that the controller includes.
1208 </p>
1209 </li>
1210 </ul></div>
1211 <div class="admonitionblock">
1212 <table><tr>
1213 <td class="icon">
1214 <img src="./images/icons/tip.png" alt="Tip" />
1215 </td>
1216 <td class="content">For more details on the rendering process, see <a href="../layouts_and_rendering.html">Layouts and Rendering in Rails</a>.</td>
1217 </tr></table>
1218 </div>
1219 <h3 id="_customizing_the_layout">6.8. Customizing the Layout</h3>
1220 <div class="para"><p>The view is only part of the story of how HTML is displayed in your web browser. Rails also has the concept of <tt>layouts</tt>, which are containers for views. When Rails renders a view to the browser, it does so by putting the view's HTML into a layout's HTML. The <tt>script/generate scaffold</tt> command automatically created a default layout, <tt>app/views/layouts/posts.html.erb</tt>, for the posts. Open this layout in your editor and modify the <tt>body</tt> tag:</p></div>
1221 <div class="listingblock">
1222 <div class="content"><!-- Generator: GNU source-highlight 2.9
1223 by Lorenzo Bettini
1224 http://www.lorenzobettini.it
1225 http://www.gnu.org/software/src-highlite -->
1226 <pre><tt><span style="color: #990000">&lt;!</span>DOCTYPE html PUBLIC <span style="color: #FF0000">"-//W3C//DTD XHTML 1.0 Transitional//EN"</span>
1227        <span style="color: #FF0000">"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"</span><span style="color: #990000">&gt;</span>
1228
1229 <span style="color: #FF0000">&lt;html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en"&gt;</span>
1230 <span style="color: #FF0000">&lt;head&gt;</span>
1231   <span style="color: #FF0000">&lt;meta http-equiv="content-type" content="text/html;charset=UTF-8" /&gt;</span>
1232   <span style="color: #FF0000">&lt;title&gt;</span>Posts<span style="color: #990000">:</span> <span style="color: #FF0000">&lt;%= controller.action_name %&gt;&lt;/title&gt;</span>
1233   <span style="color: #FF0000">&lt;%= stylesheet_link_tag 'scaffold' %&gt;</span>
1234 <span style="color: #FF0000">&lt;/head&gt;</span>
1235 <span style="color: #FF0000">&lt;body style="background: #EEEEEE;"&gt;</span>
1236
1237 <span style="color: #FF0000">&lt;p style="color: green"&gt;&lt;%= flash[:notice] %&gt;&lt;/p&gt;</span>
1238
1239 <span style="color: #FF0000">&lt;%= yield  %&gt;</span>
1240
1241 <span style="color: #FF0000">&lt;/body&gt;</span>
1242 <span style="color: #FF0000">&lt;/html&gt;</span>
1243 </tt></pre></div></div>
1244 <div class="para"><p>Now when you refresh the <tt>/posts</tt> page, you'll see a gray background to the page. This same gray background will be used throughout all the views for posts.</p></div>
1245 <h3 id="_creating_new_posts">6.9. Creating New Posts</h3>
1246 <div class="para"><p>Creating a new post involves two actions. The first is the <tt>new</tt> action, which instantiates an empty <tt>Post</tt> object:</p></div>
1247 <div class="listingblock">
1248 <div class="content"><!-- Generator: GNU source-highlight 2.9
1249 by Lorenzo Bettini
1250 http://www.lorenzobettini.it
1251 http://www.gnu.org/software/src-highlite -->
1252 <pre><tt><span style="font-weight: bold"><span style="color: #0000FF">def</span></span> new
1253   <span style="color: #009900">@post</span> <span style="color: #990000">=</span> Post<span style="color: #990000">.</span>new
1254
1255   respond_to <span style="font-weight: bold"><span style="color: #0000FF">do</span></span> <span style="color: #990000">|</span>format<span style="color: #990000">|</span>
1256     format<span style="color: #990000">.</span>html <span style="font-style: italic"><span style="color: #9A1900"># new.html.erb</span></span>
1257     format<span style="color: #990000">.</span>xml  <span style="color: #FF0000">{</span> render <span style="color: #990000">:</span>xml <span style="color: #990000">=&gt;</span> <span style="color: #009900">@post</span> <span style="color: #FF0000">}</span>
1258   <span style="font-weight: bold"><span style="color: #0000FF">end</span></span>
1259 <span style="font-weight: bold"><span style="color: #0000FF">end</span></span>
1260 </tt></pre></div></div>
1261 <div class="para"><p>The <tt>new.html.erb</tt> view displays this empty Post to the user:</p></div>
1262 <div class="listingblock">
1263 <div class="content"><!-- Generator: GNU source-highlight 2.9
1264 by Lorenzo Bettini
1265 http://www.lorenzobettini.it
1266 http://www.gnu.org/software/src-highlite -->
1267 <pre><tt><span style="color: #FF0000">&lt;h1&gt;</span>New post<span style="color: #FF0000">&lt;/h1&gt;</span>
1268
1269 <span style="color: #FF0000">&lt;% form_for(@post) do |f| %&gt;</span>
1270   <span style="color: #FF0000">&lt;%= f.error_messages %&gt;</span>
1271
1272   <span style="color: #FF0000">&lt;p&gt;</span>
1273     <span style="color: #FF0000">&lt;%= f.label :name %&gt;&lt;br /&gt;</span>
1274     <span style="color: #FF0000">&lt;%= f.text_field :name %&gt;</span>
1275   <span style="color: #FF0000">&lt;/p&gt;</span>
1276   <span style="color: #FF0000">&lt;p&gt;</span>
1277     <span style="color: #FF0000">&lt;%= f.label :title %&gt;&lt;br /&gt;</span>
1278     <span style="color: #FF0000">&lt;%= f.text_field :title %&gt;</span>
1279   <span style="color: #FF0000">&lt;/p&gt;</span>
1280   <span style="color: #FF0000">&lt;p&gt;</span>
1281     <span style="color: #FF0000">&lt;%= f.label :content %&gt;&lt;br /&gt;</span>
1282     <span style="color: #FF0000">&lt;%= f.text_area :content %&gt;</span>
1283   <span style="color: #FF0000">&lt;/p&gt;</span>
1284   <span style="color: #FF0000">&lt;p&gt;</span>
1285     <span style="color: #FF0000">&lt;%= f.submit "Create" %&gt;</span>
1286   <span style="color: #FF0000">&lt;/p&gt;</span>
1287 <span style="color: #FF0000">&lt;% end %&gt;</span>
1288
1289 <span style="color: #FF0000">&lt;%= link_to 'Back', posts_path %&gt;</span>
1290 </tt></pre></div></div>
1291 <div class="para"><p>The <tt>form_for</tt> block is used to create an HTML form. Within this block, you have access to methods to build various controls on the form. For example, <tt>f.text_field :name</tt> tells Rails to create a text input on the form, and to hook it up to the <tt>name</tt> attribute of the instance being displayed. You can only use these methods with attributes of the model that the form is based on (in this case <tt>name</tt>, <tt>title</tt>, and <tt>content</tt>). Rails uses <tt>form_for</tt> in preference to having your write raw HTML because the code is more succinct, and because it explicitly ties the form to a particular model instance.</p></div>
1292 <div class="admonitionblock">
1293 <table><tr>
1294 <td class="icon">
1295 <img src="./images/icons/tip.png" alt="Tip" />
1296 </td>
1297 <td class="content">If you need to create an HTML form that displays arbitrary fields, not tied to a model, you should use the <tt>form_tag</tt> method, which provides shortcuts for building forms that are not necessarily tied to a model instance.</td>
1298 </tr></table>
1299 </div>
1300 <div class="para"><p>When the user clicks the <tt>Create</tt> button on this form, the browser will send information back to the <tt>create</tt> method of the controller (Rails knows to call the <tt>create</tt> method because the form is sent with an HTTP POST request; that's one of the conventions that I mentioned earlier):</p></div>
1301 <div class="listingblock">
1302 <div class="content"><!-- Generator: GNU source-highlight 2.9
1303 by Lorenzo Bettini
1304 http://www.lorenzobettini.it
1305 http://www.gnu.org/software/src-highlite -->
1306 <pre><tt><span style="font-weight: bold"><span style="color: #0000FF">def</span></span> create
1307   <span style="color: #009900">@post</span> <span style="color: #990000">=</span> Post<span style="color: #990000">.</span>new<span style="color: #990000">(</span>params<span style="color: #990000">[:</span>post<span style="color: #990000">])</span>
1308
1309   respond_to <span style="font-weight: bold"><span style="color: #0000FF">do</span></span> <span style="color: #990000">|</span>format<span style="color: #990000">|</span>
1310     <span style="font-weight: bold"><span style="color: #0000FF">if</span></span> <span style="color: #009900">@post</span><span style="color: #990000">.</span>save
1311       flash<span style="color: #990000">[:</span>notice<span style="color: #990000">]</span> <span style="color: #990000">=</span> <span style="color: #FF0000">'Post was successfully created.'</span>
1312       format<span style="color: #990000">.</span>html <span style="color: #FF0000">{</span> redirect_to<span style="color: #990000">(</span><span style="color: #009900">@post</span><span style="color: #990000">)</span> <span style="color: #FF0000">}</span>
1313       format<span style="color: #990000">.</span>xml  <span style="color: #FF0000">{</span> render <span style="color: #990000">:</span>xml <span style="color: #990000">=&gt;</span> <span style="color: #009900">@post</span><span style="color: #990000">,</span> <span style="color: #990000">:</span>status <span style="color: #990000">=&gt;</span> <span style="color: #990000">:</span>created<span style="color: #990000">,</span> <span style="color: #990000">:</span>location <span style="color: #990000">=&gt;</span> <span style="color: #009900">@post</span> <span style="color: #FF0000">}</span>
1314     <span style="font-weight: bold"><span style="color: #0000FF">else</span></span>
1315       format<span style="color: #990000">.</span>html <span style="color: #FF0000">{</span> render <span style="color: #990000">:</span>action <span style="color: #990000">=&gt;</span> <span style="color: #FF0000">"new"</span> <span style="color: #FF0000">}</span>
1316       format<span style="color: #990000">.</span>xml  <span style="color: #FF0000">{</span> render <span style="color: #990000">:</span>xml <span style="color: #990000">=&gt;</span> <span style="color: #009900">@post</span><span style="color: #990000">.</span>errors<span style="color: #990000">,</span> <span style="color: #990000">:</span>status <span style="color: #990000">=&gt;</span> <span style="color: #990000">:</span>unprocessable_entity <span style="color: #FF0000">}</span>
1317     <span style="font-weight: bold"><span style="color: #0000FF">end</span></span>
1318   <span style="font-weight: bold"><span style="color: #0000FF">end</span></span>
1319 <span style="font-weight: bold"><span style="color: #0000FF">end</span></span>
1320 </tt></pre></div></div>
1321 <div class="para"><p>The <tt>create</tt> action instantiates a new Post object from the data supplied by the user on the form, which Rails makes available in the <tt>params</tt> hash. After saving the new post, it uses <tt>flash[:notice]</tt> to create an informational message for the user, and redirects to the show action for the post. If there's any problem, the <tt>create</tt> action just shows the <tt>new</tt> view a second time, with any error messages.</p></div>
1322 <div class="para"><p>Rails provides the <tt>flash</tt> hash (usually just called the Flash) so that messages can be carried over to another action, providing the user with useful information on the status of their request.  In the case of <tt>create</tt>, the user never actually sees any page rendered during the Post creation process, because it immediately redirects to the new Post as soon Rails saves the record. The Flash carries over a message to the next action, so that when the user is redirected back to the <tt>show</tt> action, they are presented with a message saying "Post was successfully created."</p></div>
1323 <h3 id="_showing_an_individual_post">6.10. Showing an Individual Post</h3>
1324 <div class="para"><p>When you click the <tt>show</tt> link for a post on the index page, it will bring you to a URL like <tt>http://localhost:3000/posts/1</tt>. Rails interprets this as a call to the <tt>show</tt> action for the resource, and passes in <tt>1</tt> as the <tt>:id</tt> parameter. Here's the <tt>show</tt> action:</p></div>
1325 <div class="listingblock">
1326 <div class="content"><!-- Generator: GNU source-highlight 2.9
1327 by Lorenzo Bettini
1328 http://www.lorenzobettini.it
1329 http://www.gnu.org/software/src-highlite -->
1330 <pre><tt><span style="font-weight: bold"><span style="color: #0000FF">def</span></span> show
1331   <span style="color: #009900">@post</span> <span style="color: #990000">=</span> Post<span style="color: #990000">.</span>find<span style="color: #990000">(</span>params<span style="color: #990000">[:</span>id<span style="color: #990000">])</span>
1332
1333   respond_to <span style="font-weight: bold"><span style="color: #0000FF">do</span></span> <span style="color: #990000">|</span>format<span style="color: #990000">|</span>
1334     format<span style="color: #990000">.</span>html <span style="font-style: italic"><span style="color: #9A1900"># show.html.erb</span></span>
1335     format<span style="color: #990000">.</span>xml  <span style="color: #FF0000">{</span> render <span style="color: #990000">:</span>xml <span style="color: #990000">=&gt;</span> <span style="color: #009900">@post</span> <span style="color: #FF0000">}</span>
1336   <span style="font-weight: bold"><span style="color: #0000FF">end</span></span>
1337 <span style="font-weight: bold"><span style="color: #0000FF">end</span></span>
1338 </tt></pre></div></div>
1339 <div class="para"><p>The <tt>show</tt> action uses <tt>Post.find</tt> to search for a single record in the database by its id value. After finding the record, Rails displays it by using <tt>show.html.erb</tt>:</p></div>
1340 <div class="listingblock">
1341 <div class="content"><!-- Generator: GNU source-highlight 2.9
1342 by Lorenzo Bettini
1343 http://www.lorenzobettini.it
1344 http://www.gnu.org/software/src-highlite -->
1345 <pre><tt><span style="color: #FF0000">&lt;p&gt;</span>
1346   <span style="color: #FF0000">&lt;b&gt;</span>Name<span style="color: #990000">:</span><span style="color: #FF0000">&lt;/b&gt;</span>
1347   <span style="color: #FF0000">&lt;%=h @post.name %&gt;</span>
1348 <span style="color: #FF0000">&lt;/p&gt;</span>
1349
1350 <span style="color: #FF0000">&lt;p&gt;</span>
1351   <span style="color: #FF0000">&lt;b&gt;</span>Title<span style="color: #990000">:</span><span style="color: #FF0000">&lt;/b&gt;</span>
1352   <span style="color: #FF0000">&lt;%=h @post.title %&gt;</span>
1353 <span style="color: #FF0000">&lt;/p&gt;</span>
1354
1355 <span style="color: #FF0000">&lt;p&gt;</span>
1356   <span style="color: #FF0000">&lt;b&gt;</span>Content<span style="color: #990000">:</span><span style="color: #FF0000">&lt;/b&gt;</span>
1357   <span style="color: #FF0000">&lt;%=h @post.content %&gt;</span>
1358 <span style="color: #FF0000">&lt;/p&gt;</span>
1359
1360
1361 <span style="color: #FF0000">&lt;%= link_to 'Edit', edit_post_path(@post) %&gt;</span> <span style="color: #990000">|</span>
1362 <span style="color: #FF0000">&lt;%= link_to 'Back', posts_path %&gt;</span>
1363 </tt></pre></div></div>
1364 <h3 id="_editing_posts">6.11. Editing Posts</h3>
1365 <div class="para"><p>Like creating a new post, editing a post is a two-part process. The first step is a request to <tt>edit_post_path(@post)</tt> with a particular post. This calls the <tt>edit</tt> action in the controller:</p></div>
1366 <div class="listingblock">
1367 <div class="content"><!-- Generator: GNU source-highlight 2.9
1368 by Lorenzo Bettini
1369 http://www.lorenzobettini.it
1370 http://www.gnu.org/software/src-highlite -->
1371 <pre><tt><span style="font-weight: bold"><span style="color: #0000FF">def</span></span> edit
1372   <span style="color: #009900">@post</span> <span style="color: #990000">=</span> Post<span style="color: #990000">.</span>find<span style="color: #990000">(</span>params<span style="color: #990000">[:</span>id<span style="color: #990000">])</span>
1373 <span style="font-weight: bold"><span style="color: #0000FF">end</span></span>
1374 </tt></pre></div></div>
1375 <div class="para"><p>After finding the requested post, Rails uses the <tt>edit.html.erb</tt> view to display it:</p></div>
1376 <div class="listingblock">
1377 <div class="content"><!-- Generator: GNU source-highlight 2.9
1378 by Lorenzo Bettini
1379 http://www.lorenzobettini.it
1380 http://www.gnu.org/software/src-highlite -->
1381 <pre><tt><span style="color: #FF0000">&lt;h1&gt;</span>Editing post<span style="color: #FF0000">&lt;/h1&gt;</span>
1382
1383 <span style="color: #FF0000">&lt;% form_for(@post) do |f| %&gt;</span>
1384   <span style="color: #FF0000">&lt;%= f.error_messages %&gt;</span>
1385
1386   <span style="color: #FF0000">&lt;p&gt;</span>
1387     <span style="color: #FF0000">&lt;%= f.label :name %&gt;&lt;br /&gt;</span>
1388     <span style="color: #FF0000">&lt;%= f.text_field :name %&gt;</span>
1389   <span style="color: #FF0000">&lt;/p&gt;</span>
1390   <span style="color: #FF0000">&lt;p&gt;</span>
1391     <span style="color: #FF0000">&lt;%= f.label :title %&gt;&lt;br /&gt;</span>
1392     <span style="color: #FF0000">&lt;%= f.text_field :title %&gt;</span>
1393   <span style="color: #FF0000">&lt;/p&gt;</span>
1394   <span style="color: #FF0000">&lt;p&gt;</span>
1395     <span style="color: #FF0000">&lt;%= f.label :content %&gt;&lt;br /&gt;</span>
1396     <span style="color: #FF0000">&lt;%= f.text_area :content %&gt;</span>
1397   <span style="color: #FF0000">&lt;/p&gt;</span>
1398   <span style="color: #FF0000">&lt;p&gt;</span>
1399     <span style="color: #FF0000">&lt;%= f.submit "Update" %&gt;</span>
1400   <span style="color: #FF0000">&lt;/p&gt;</span>
1401 <span style="color: #FF0000">&lt;% end %&gt;</span>
1402
1403 <span style="color: #FF0000">&lt;%= link_to 'Show', @post %&gt;</span> <span style="color: #990000">|</span>
1404 <span style="color: #FF0000">&lt;%= link_to 'Back', posts_path %&gt;</span>
1405 </tt></pre></div></div>
1406 <div class="para"><p>Submitting the form created by this view will invoke the <tt>update</tt> action within the controller:</p></div>
1407 <div class="listingblock">
1408 <div class="content"><!-- Generator: GNU source-highlight 2.9
1409 by Lorenzo Bettini
1410 http://www.lorenzobettini.it
1411 http://www.gnu.org/software/src-highlite -->
1412 <pre><tt><span style="font-weight: bold"><span style="color: #0000FF">def</span></span> update
1413   <span style="color: #009900">@post</span> <span style="color: #990000">=</span> Post<span style="color: #990000">.</span>find<span style="color: #990000">(</span>params<span style="color: #990000">[:</span>id<span style="color: #990000">])</span>
1414
1415   respond_to <span style="font-weight: bold"><span style="color: #0000FF">do</span></span> <span style="color: #990000">|</span>format<span style="color: #990000">|</span>
1416     <span style="font-weight: bold"><span style="color: #0000FF">if</span></span> <span style="color: #009900">@post</span><span style="color: #990000">.</span>update_attributes<span style="color: #990000">(</span>params<span style="color: #990000">[:</span>post<span style="color: #990000">])</span>
1417       flash<span style="color: #990000">[:</span>notice<span style="color: #990000">]</span> <span style="color: #990000">=</span> <span style="color: #FF0000">'Post was successfully updated.'</span>
1418       format<span style="color: #990000">.</span>html <span style="color: #FF0000">{</span> redirect_to<span style="color: #990000">(</span><span style="color: #009900">@post</span><span style="color: #990000">)</span> <span style="color: #FF0000">}</span>
1419       format<span style="color: #990000">.</span>xml  <span style="color: #FF0000">{</span> head <span style="color: #990000">:</span>ok <span style="color: #FF0000">}</span>
1420     <span style="font-weight: bold"><span style="color: #0000FF">else</span></span>
1421       format<span style="color: #990000">.</span>html <span style="color: #FF0000">{</span> render <span style="color: #990000">:</span>action <span style="color: #990000">=&gt;</span> <span style="color: #FF0000">"edit"</span> <span style="color: #FF0000">}</span>
1422       format<span style="color: #990000">.</span>xml  <span style="color: #FF0000">{</span> render <span style="color: #990000">:</span>xml <span style="color: #990000">=&gt;</span> <span style="color: #009900">@post</span><span style="color: #990000">.</span>errors<span style="color: #990000">,</span> <span style="color: #990000">:</span>status <span style="color: #990000">=&gt;</span> <span style="color: #990000">:</span>unprocessable_entity <span style="color: #FF0000">}</span>
1423     <span style="font-weight: bold"><span style="color: #0000FF">end</span></span>
1424   <span style="font-weight: bold"><span style="color: #0000FF">end</span></span>
1425 <span style="font-weight: bold"><span style="color: #0000FF">end</span></span>
1426 </tt></pre></div></div>
1427 <div class="para"><p>In the <tt>update</tt> action, Rails first uses the <tt>:id</tt> parameter passed back from the edit view to locate the database record that's being edited. The <tt>update_attributes</tt> call then takes the rest of the parameters from the request and applies them to this record. If all goes well, the user is redirected to the post's <tt>show</tt> view. If there are any problems, it's back to <tt>edit</tt> to correct them.</p></div>
1428 <div class="admonitionblock">
1429 <table><tr>
1430 <td class="icon">
1431 <img src="./images/icons/note.png" alt="Note" />
1432 </td>
1433 <td class="content">Sharp-eyed readers will have noticed that the <tt>form_for</tt> declaration is identical for the <tt>new</tt> and <tt>edit</tt> views. Rails generates different code for the two forms because it's smart enough to notice that in the one case it's being passed a new record that has never been saved, and in the other case an existing record that has already been saved to the database. In a production Rails application, you would ordinarily eliminate this duplication by moving identical code to a <em>partial template</em>, which you could then include in both parent templates. But the scaffold generator tries not to make too many assumptions, and generates code that’s easy to modify if you want different forms for <tt>create</tt> and <tt>edit</tt>.</td>
1434 </tr></table>
1435 </div>
1436 <h3 id="_destroying_a_post">6.12. Destroying a Post</h3>
1437 <div class="para"><p>Finally, clicking one of the <tt>destroy</tt> links sends the associated id to the <tt>destroy</tt> action:</p></div>
1438 <div class="listingblock">
1439 <div class="content"><!-- Generator: GNU source-highlight 2.9
1440 by Lorenzo Bettini
1441 http://www.lorenzobettini.it
1442 http://www.gnu.org/software/src-highlite -->
1443 <pre><tt><span style="font-weight: bold"><span style="color: #0000FF">def</span></span> destroy
1444   <span style="color: #009900">@post</span> <span style="color: #990000">=</span> Post<span style="color: #990000">.</span>find<span style="color: #990000">(</span>params<span style="color: #990000">[:</span>id<span style="color: #990000">])</span>
1445   <span style="color: #009900">@post</span><span style="color: #990000">.</span>destroy
1446
1447   respond_to <span style="font-weight: bold"><span style="color: #0000FF">do</span></span> <span style="color: #990000">|</span>format<span style="color: #990000">|</span>
1448     format<span style="color: #990000">.</span>html <span style="color: #FF0000">{</span> redirect_to<span style="color: #990000">(</span>posts_url<span style="color: #990000">)</span> <span style="color: #FF0000">}</span>
1449     format<span style="color: #990000">.</span>xml  <span style="color: #FF0000">{</span> head <span style="color: #990000">:</span>ok <span style="color: #FF0000">}</span>
1450   <span style="font-weight: bold"><span style="color: #0000FF">end</span></span>
1451 <span style="font-weight: bold"><span style="color: #0000FF">end</span></span>
1452 </tt></pre></div></div>
1453 <div class="para"><p>The <tt>destroy</tt> method of an Active Record model instance removes the corresponding record from the database. After that's done, there isn't any record to display, so Rails redirects the user's browser to the index view for the model.</p></div>
1454 </div>
1455 <h2 id="_drying_up_the_code">7. DRYing up the Code</h2>
1456 <div class="sectionbody">
1457 <div class="para"><p>At this point, it’s worth looking at some of the tools that Rails provides to eliminate duplication in your code. In particular, you can use <em>partials</em> to clean up duplication in views and <em>filters</em> to help with duplication in controllers.</p></div>
1458 <h3 id="_using_partials_to_eliminate_view_duplication">7.1. Using Partials to Eliminate View Duplication</h3>
1459 <div class="para"><p>As you saw earlier, the scaffold-generated views for the <tt>new</tt> and <tt>edit</tt> actions are largely identical. You can pull the shared code out into a <tt>partial</tt> template. This requires editing the new and edit views, and adding a new template:</p></div>
1460 <div class="para"><p><tt>new.html.erb</tt>:</p></div>
1461 <div class="listingblock">
1462 <div class="content"><!-- Generator: GNU source-highlight 2.9
1463 by Lorenzo Bettini
1464 http://www.lorenzobettini.it
1465 http://www.gnu.org/software/src-highlite -->
1466 <pre><tt><span style="color: #FF0000">&lt;h1&gt;</span>New post<span style="color: #FF0000">&lt;/h1&gt;</span>
1467
1468 <span style="color: #FF0000">&lt;%= render :partial =&gt;</span> <span style="color: #FF0000">"form"</span> <span style="color: #990000">%&gt;</span>
1469
1470 <span style="color: #FF0000">&lt;%= link_to 'Back', posts_path %&gt;</span>
1471 </tt></pre></div></div>
1472 <div class="para"><p><tt>edit.html.erb</tt>:</p></div>
1473 <div class="listingblock">
1474 <div class="content"><!-- Generator: GNU source-highlight 2.9
1475 by Lorenzo Bettini
1476 http://www.lorenzobettini.it
1477 http://www.gnu.org/software/src-highlite -->
1478 <pre><tt><span style="color: #FF0000">&lt;h1&gt;</span>Editing post<span style="color: #FF0000">&lt;/h1&gt;</span>
1479
1480 <span style="color: #FF0000">&lt;%= render :partial =&gt;</span> <span style="color: #FF0000">"form"</span> <span style="color: #990000">%&gt;</span>
1481
1482 <span style="color: #FF0000">&lt;%= link_to 'Show', @post %&gt;</span> <span style="color: #990000">|</span>
1483 <span style="color: #FF0000">&lt;%= link_to 'Back', posts_path %&gt;</span>
1484 </tt></pre></div></div>
1485 <div class="para"><p><tt>_form.html.erb</tt>:</p></div>
1486 <div class="listingblock">
1487 <div class="content"><!-- Generator: GNU source-highlight 2.9
1488 by Lorenzo Bettini
1489 http://www.lorenzobettini.it
1490 http://www.gnu.org/software/src-highlite -->
1491 <pre><tt><span style="color: #FF0000">&lt;% form_for(@post) do |f| %&gt;</span>
1492   <span style="color: #FF0000">&lt;%= f.error_messages %&gt;</span>
1493
1494   <span style="color: #FF0000">&lt;p&gt;</span>
1495     <span style="color: #FF0000">&lt;%= f.label :name %&gt;&lt;br /&gt;</span>
1496     <span style="color: #FF0000">&lt;%= f.text_field :name %&gt;</span>
1497   <span style="color: #FF0000">&lt;/p&gt;</span>
1498   <span style="color: #FF0000">&lt;p&gt;</span>
1499     <span style="color: #FF0000">&lt;%= f.label :title, "title" %&gt;&lt;br /&gt;</span>
1500     <span style="color: #FF0000">&lt;%= f.text_field :title %&gt;</span>
1501   <span style="color: #FF0000">&lt;/p&gt;</span>
1502   <span style="color: #FF0000">&lt;p&gt;</span>
1503     <span style="color: #FF0000">&lt;%= f.label :content %&gt;&lt;br /&gt;</span>
1504     <span style="color: #FF0000">&lt;%= f.text_area :content %&gt;</span>
1505   <span style="color: #FF0000">&lt;/p&gt;</span>
1506   <span style="color: #FF0000">&lt;p&gt;</span>
1507     <span style="color: #FF0000">&lt;%= f.submit "Save" %&gt;</span>
1508   <span style="color: #FF0000">&lt;/p&gt;</span>
1509 <span style="color: #FF0000">&lt;% end %&gt;</span>
1510 </tt></pre></div></div>
1511 <div class="para"><p>Now, when Rails renders the <tt>new</tt> or <tt>edit</tt> view, it will insert the <tt>_form</tt> partial at the indicated point. Note the naming convention for partials: if you refer to a partial named <tt>form</tt> inside of a view, the corresponding file is <tt>_form.html.erb</tt>, with a leading underscore.</p></div>
1512 <div class="para"><p>For more information on partials, refer to the <a href="../layouts_and_rendering.html">Layouts and Rending in Rails</a> guide.</p></div>
1513 <h3 id="_using_filters_to_eliminate_controller_duplication">7.2. Using Filters to Eliminate Controller Duplication</h3>
1514 <div class="para"><p>At this point, if you look at the controller for posts, you’ll see some duplication:</p></div>
1515 <div class="listingblock">
1516 <div class="content"><!-- Generator: GNU source-highlight 2.9
1517 by Lorenzo Bettini
1518 http://www.lorenzobettini.it
1519 http://www.gnu.org/software/src-highlite -->
1520 <pre><tt><span style="font-weight: bold"><span style="color: #0000FF">class</span></span> PostsController <span style="color: #990000">&lt;</span> ApplicationController
1521   <span style="font-style: italic"><span style="color: #9A1900"># ...</span></span>
1522   <span style="font-weight: bold"><span style="color: #0000FF">def</span></span> show
1523     <span style="color: #009900">@post</span> <span style="color: #990000">=</span> Post<span style="color: #990000">.</span>find<span style="color: #990000">(</span>params<span style="color: #990000">[:</span>id<span style="color: #990000">])</span>
1524         <span style="font-style: italic"><span style="color: #9A1900"># ...</span></span>
1525   <span style="font-weight: bold"><span style="color: #0000FF">end</span></span>
1526
1527   <span style="font-weight: bold"><span style="color: #0000FF">def</span></span> edit
1528     <span style="color: #009900">@post</span> <span style="color: #990000">=</span> Post<span style="color: #990000">.</span>find<span style="color: #990000">(</span>params<span style="color: #990000">[:</span>id<span style="color: #990000">])</span>
1529   <span style="font-weight: bold"><span style="color: #0000FF">end</span></span>
1530
1531   <span style="font-weight: bold"><span style="color: #0000FF">def</span></span> update
1532     <span style="color: #009900">@post</span> <span style="color: #990000">=</span> Post<span style="color: #990000">.</span>find<span style="color: #990000">(</span>params<span style="color: #990000">[:</span>id<span style="color: #990000">])</span>
1533     <span style="font-style: italic"><span style="color: #9A1900"># ...</span></span>
1534   <span style="font-weight: bold"><span style="color: #0000FF">end</span></span>
1535
1536   <span style="font-weight: bold"><span style="color: #0000FF">def</span></span> destroy
1537     <span style="color: #009900">@post</span> <span style="color: #990000">=</span> Post<span style="color: #990000">.</span>find<span style="color: #990000">(</span>params<span style="color: #990000">[:</span>id<span style="color: #990000">])</span>
1538     <span style="font-style: italic"><span style="color: #9A1900"># ...</span></span>
1539   <span style="font-weight: bold"><span style="color: #0000FF">end</span></span>
1540 <span style="font-weight: bold"><span style="color: #0000FF">end</span></span>
1541 </tt></pre></div></div>
1542 <div class="para"><p>Four instances of the exact same line of code doesn’t seem very DRY. Rails provides <em>filters</em> as a way to address this sort of repeated code. In this case, you can DRY things up by using a <tt>before_filter</tt>:</p></div>
1543 <div class="listingblock">
1544 <div class="content"><!-- Generator: GNU source-highlight 2.9
1545 by Lorenzo Bettini
1546 http://www.lorenzobettini.it
1547 http://www.gnu.org/software/src-highlite -->
1548 <pre><tt><span style="font-weight: bold"><span style="color: #0000FF">class</span></span> PostsController <span style="color: #990000">&lt;</span> ApplicationController
1549   before_filter <span style="color: #990000">:</span>find_post<span style="color: #990000">,</span> <span style="color: #990000">:</span>only <span style="color: #990000">=&gt;</span> <span style="color: #990000">[:</span>show<span style="color: #990000">,</span> <span style="color: #990000">:</span>edit<span style="color: #990000">,</span> <span style="color: #990000">:</span>update<span style="color: #990000">,</span> <span style="color: #990000">:</span>destroy<span style="color: #990000">]</span>
1550   <span style="font-style: italic"><span style="color: #9A1900"># ...</span></span>
1551   <span style="font-weight: bold"><span style="color: #0000FF">def</span></span> show
1552         <span style="font-style: italic"><span style="color: #9A1900"># ...</span></span>
1553   <span style="font-weight: bold"><span style="color: #0000FF">end</span></span>
1554
1555   <span style="font-weight: bold"><span style="color: #0000FF">def</span></span> edit
1556   <span style="font-weight: bold"><span style="color: #0000FF">end</span></span>
1557
1558   <span style="font-weight: bold"><span style="color: #0000FF">def</span></span> update
1559     <span style="font-style: italic"><span style="color: #9A1900"># ...</span></span>
1560   <span style="font-weight: bold"><span style="color: #0000FF">end</span></span>
1561
1562   <span style="font-weight: bold"><span style="color: #0000FF">def</span></span> destroy
1563     <span style="font-style: italic"><span style="color: #9A1900"># ...</span></span>
1564   <span style="font-weight: bold"><span style="color: #0000FF">end</span></span>
1565
1566   private
1567     <span style="font-weight: bold"><span style="color: #0000FF">def</span></span> find_post
1568       <span style="color: #009900">@post</span> <span style="color: #990000">=</span> Post<span style="color: #990000">.</span>find<span style="color: #990000">(</span>params<span style="color: #990000">[:</span>id<span style="color: #990000">])</span>
1569     <span style="font-weight: bold"><span style="color: #0000FF">end</span></span>
1570 <span style="font-weight: bold"><span style="color: #0000FF">end</span></span>
1571 </tt></pre></div></div>
1572 <div class="para"><p>Rails runs <em>before filters</em> before any action in the controller. You can use the <tt>:only</tt> clause to limit a before filter to only certain actions, or an <tt>:except</tt> clause to specifically skip a before filter for certain actions. Rails also allows you to define <em>after filters</em> that run after processing an action, as well as <em>around filters</em> that surround the processing of actions. Filters can also be defined in external classes to make it easy to share them between controllers.</p></div>
1573 <div class="para"><p>For more information on filters, see the <a href="actioncontroller_basics.html">Action Controller Basics</a> guide.</p></div>
1574 </div>
1575 <h2 id="_adding_a_second_model">8. Adding a Second Model</h2>
1576 <div class="sectionbody">
1577 <div class="para"><p>Now that you've seen what's in a model built with scaffolding, it's time to add a second model to the application. The second model will handle comments on blog posts.</p></div>
1578 <h3 id="_generating_a_model">8.1. Generating a Model</h3>
1579 <div class="para"><p>Models in Rails use a singular name, and their corresponding database tables use a plural name. For the model to hold comments, the convention is to use the name Comment. Even if you don't want to use the entire apparatus set up by scaffolding, most Rails developers still use generators to make things like models and controllers. To create the new model, run this command in your terminal:</p></div>
1580 <div class="listingblock">
1581 <div class="content"><!-- Generator: GNU source-highlight 2.9
1582 by Lorenzo Bettini
1583 http://www.lorenzobettini.it
1584 http://www.gnu.org/software/src-highlite -->
1585 <pre><tt>$ script/generate model Comment commenter<span style="color: #990000">:</span>string body<span style="color: #990000">:</span>text post<span style="color: #990000">:</span>references
1586 </tt></pre></div></div>
1587 <div class="para"><p>This command will generate four files:</p></div>
1588 <div class="ilist"><ul>
1589 <li>
1590 <p>
1591 <tt>app/models/comment.rb</tt> - The model
1592 </p>
1593 </li>
1594 <li>
1595 <p>
1596 +db/migrate/20081013214407_create_comments.rb - The migration
1597 </p>
1598 </li>
1599 <li>
1600 <p>
1601 <tt>test/unit/comment_test.rb</tt> and <tt>test/fixtures/comments.yml</tt> - The test harness.
1602 </p>
1603 </li>
1604 </ul></div>
1605 <div class="para"><p>First, take a look at <tt>comment.rb</tt>:</p></div>
1606 <div class="listingblock">
1607 <div class="content"><!-- Generator: GNU source-highlight 2.9
1608 by Lorenzo Bettini
1609 http://www.lorenzobettini.it
1610 http://www.gnu.org/software/src-highlite -->
1611 <pre><tt><span style="font-weight: bold"><span style="color: #0000FF">class</span></span> Comment <span style="color: #990000">&lt;</span> ActiveRecord<span style="color: #990000">::</span>Base
1612   belongs_to <span style="color: #990000">:</span>post
1613 <span style="font-weight: bold"><span style="color: #0000FF">end</span></span>
1614 </tt></pre></div></div>
1615 <div class="para"><p>This is very similar to the <tt>post.rb</tt> model that you saw earlier. The difference is the line <tt>belongs_to :post</tt>, which sets up an Active Record <em>association</em>. You'll learn a little about associations in the next section of this guide.</p></div>
1616 <div class="para"><p>In addition to the model, Rails has also made a migration to create the corresponding database table:</p></div>
1617 <div class="listingblock">
1618 <div class="content"><!-- Generator: GNU source-highlight 2.9
1619 by Lorenzo Bettini
1620 http://www.lorenzobettini.it
1621 http://www.gnu.org/software/src-highlite -->
1622 <pre><tt><span style="font-weight: bold"><span style="color: #0000FF">class</span></span> CreateComments <span style="color: #990000">&lt;</span> ActiveRecord<span style="color: #990000">::</span>Migration
1623   <span style="font-weight: bold"><span style="color: #0000FF">def</span></span> <span style="font-weight: bold"><span style="color: #0000FF">self</span></span><span style="color: #990000">.</span>up
1624     create_table <span style="color: #990000">:</span>comments <span style="font-weight: bold"><span style="color: #0000FF">do</span></span> <span style="color: #990000">|</span>t<span style="color: #990000">|</span>
1625       t<span style="color: #990000">.</span>string <span style="color: #990000">:</span>commenter
1626       t<span style="color: #990000">.</span>text <span style="color: #990000">:</span>body
1627       t<span style="color: #990000">.</span>references <span style="color: #990000">:</span>post
1628
1629       t<span style="color: #990000">.</span>timestamps
1630     <span style="font-weight: bold"><span style="color: #0000FF">end</span></span>
1631   <span style="font-weight: bold"><span style="color: #0000FF">end</span></span>
1632
1633   <span style="font-weight: bold"><span style="color: #0000FF">def</span></span> <span style="font-weight: bold"><span style="color: #0000FF">self</span></span><span style="color: #990000">.</span>down
1634     drop_table <span style="color: #990000">:</span>comments
1635   <span style="font-weight: bold"><span style="color: #0000FF">end</span></span>
1636 <span style="font-weight: bold"><span style="color: #0000FF">end</span></span>
1637 </tt></pre></div></div>
1638 <div class="para"><p>The <tt>t.references</tt> line sets up a foreign key column for the association between the two models. Go ahead and run the migration:</p></div>
1639 <div class="listingblock">
1640 <div class="content"><!-- Generator: GNU source-highlight 2.9
1641 by Lorenzo Bettini
1642 http://www.lorenzobettini.it
1643 http://www.gnu.org/software/src-highlite -->
1644 <pre><tt>$ rake db<span style="color: #990000">:</span>migrate
1645 </tt></pre></div></div>
1646 <div class="para"><p>Rails is smart enough to only execute the migrations that have not already been run against this particular database.</p></div>
1647 <h3 id="_associating_models">8.2. Associating Models</h3>
1648 <div class="para"><p>Active Record associations let you easily declare the relationship between two models. In the case of comments and posts, you could write out the relationships this way:</p></div>
1649 <div class="ilist"><ul>
1650 <li>
1651 <p>
1652 Each comment belongs to one post
1653 </p>
1654 </li>
1655 <li>
1656 <p>
1657 One post can have many comments
1658 </p>
1659 </li>
1660 </ul></div>
1661 <div class="para"><p>In fact, this is very close to the syntax that Rails uses to declare this association. You've already seen the line of code inside the Comment model that makes each comment belong to a Post:</p></div>
1662 <div class="listingblock">
1663 <div class="content"><!-- Generator: GNU source-highlight 2.9
1664 by Lorenzo Bettini
1665 http://www.lorenzobettini.it
1666 http://www.gnu.org/software/src-highlite -->
1667 <pre><tt><span style="font-weight: bold"><span style="color: #0000FF">class</span></span> Comment <span style="color: #990000">&lt;</span> ActiveRecord<span style="color: #990000">::</span>Base
1668   belongs_to <span style="color: #990000">:</span>post
1669 <span style="font-weight: bold"><span style="color: #0000FF">end</span></span>
1670 </tt></pre></div></div>
1671 <div class="para"><p>You'll need to edit the <tt>post.rb</tt> file to add the other side of the association:</p></div>
1672 <div class="listingblock">
1673 <div class="content"><!-- Generator: GNU source-highlight 2.9
1674 by Lorenzo Bettini
1675 http://www.lorenzobettini.it
1676 http://www.gnu.org/software/src-highlite -->
1677 <pre><tt><span style="font-weight: bold"><span style="color: #0000FF">class</span></span> Post <span style="color: #990000">&lt;</span> ActiveRecord<span style="color: #990000">::</span>Base
1678   validates_presence_of <span style="color: #990000">:</span>name<span style="color: #990000">,</span> <span style="color: #990000">:</span>title
1679   validates_length_of <span style="color: #990000">:</span>title<span style="color: #990000">,</span> <span style="color: #990000">:</span>minimum <span style="color: #990000">=&gt;</span> <span style="color: #993399">5</span>
1680   has_many <span style="color: #990000">:</span>comments
1681 <span style="font-weight: bold"><span style="color: #0000FF">end</span></span>
1682 </tt></pre></div></div>
1683 <div class="para"><p>These two declarations enable a good bit of automatic behavior. For example, if you have an instance variable <tt>@post</tt> containing a post, you can retrieve all the comments belonging to that post as the array <tt>@post.comments</tt>.</p></div>
1684 <div class="admonitionblock">
1685 <table><tr>
1686 <td class="icon">
1687 <img src="./images/icons/tip.png" alt="Tip" />
1688 </td>
1689 <td class="content">For more information on Active Record associations, see the <a href="../association_basics.html">Active Record Associations</a> guide.</td>
1690 </tr></table>
1691 </div>
1692 <h3 id="_adding_a_route">8.3. Adding a Route</h3>
1693 <div class="para"><p><em>Routes</em> are entries in the <tt>config/routes.rb</tt> file that tell Rails how to match incoming HTTP requests to controller actions. Open up that file and find the existing line referring to <tt>posts</tt>. Then edit it as follows:</p></div>
1694 <div class="listingblock">
1695 <div class="content"><!-- Generator: GNU source-highlight 2.9
1696 by Lorenzo Bettini
1697 http://www.lorenzobettini.it
1698 http://www.gnu.org/software/src-highlite -->
1699 <pre><tt>map<span style="color: #990000">.</span>resources <span style="color: #990000">:</span>posts <span style="font-weight: bold"><span style="color: #0000FF">do</span></span> <span style="color: #990000">|</span>post<span style="color: #990000">|</span>
1700   post<span style="color: #990000">.</span>resources <span style="color: #990000">:</span>comments
1701 <span style="font-weight: bold"><span style="color: #0000FF">end</span></span>
1702 </tt></pre></div></div>
1703 <div class="para"><p>This creates <tt>comments</tt> as a <em>nested resource</em> within <tt>posts</tt>. This is another part of capturing the hierarchical relationship that exists between posts and comments.</p></div>
1704 <div class="admonitionblock">
1705 <table><tr>
1706 <td class="icon">
1707 <img src="./images/icons/tip.png" alt="Tip" />
1708 </td>
1709 <td class="content">For more information on routing, see the <a href="../routing_outside_in">Rails Routing from the Outside In</a> guide.</td>
1710 </tr></table>
1711 </div>
1712 <h3 id="_generating_a_controller">8.4. Generating a Controller</h3>
1713 <div class="para"><p>With the model in hand, you can turn your attention to creating a matching controller. Again, there's a generator for this:</p></div>
1714 <div class="listingblock">
1715 <div class="content"><!-- Generator: GNU source-highlight 2.9
1716 by Lorenzo Bettini
1717 http://www.lorenzobettini.it
1718 http://www.gnu.org/software/src-highlite -->
1719 <pre><tt>$ script/generate controller Comments index show new edit
1720 </tt></pre></div></div>
1721 <div class="para"><p>This creates seven files:</p></div>
1722 <div class="ilist"><ul>
1723 <li>
1724 <p>
1725 <tt>app/controllers/comments_controller.rb</tt> - The controller
1726 </p>
1727 </li>
1728 <li>
1729 <p>
1730 <tt>app/helpers/comments_helper.rb</tt> - A view helper file
1731 </p>
1732 </li>
1733 <li>
1734 <p>
1735 <tt>app/views/comments/index.html.erb</tt> - The view for the index action
1736 </p>
1737 </li>
1738 <li>
1739 <p>
1740 <tt>app/views/comments/show.html.erb</tt> - The view for the show action
1741 </p>
1742 </li>
1743 <li>
1744 <p>
1745 <tt>app/views/comments/new.html.erb</tt> - The view for the new action
1746 </p>
1747 </li>
1748 <li>
1749 <p>
1750 <tt>app/views/comments/edit.html.erb</tt> - The view for the edit action
1751 </p>
1752 </li>
1753 <li>
1754 <p>
1755 <tt>test/functional/comments_controller_test.rb</tt> - The functional tests for the controller
1756 </p>
1757 </li>
1758 </ul></div>
1759 <div class="para"><p>The controller will be generated with empty methods for each action that you specified in the call to <tt>script/generate controller</tt>:</p></div>
1760 <div class="listingblock">
1761 <div class="content"><!-- Generator: GNU source-highlight 2.9
1762 by Lorenzo Bettini
1763 http://www.lorenzobettini.it
1764 http://www.gnu.org/software/src-highlite -->
1765 <pre><tt><span style="font-weight: bold"><span style="color: #0000FF">class</span></span> CommentsController <span style="color: #990000">&lt;</span> ApplicationController
1766   <span style="font-weight: bold"><span style="color: #0000FF">def</span></span> index
1767   <span style="font-weight: bold"><span style="color: #0000FF">end</span></span>
1768
1769   <span style="font-weight: bold"><span style="color: #0000FF">def</span></span> show
1770   <span style="font-weight: bold"><span style="color: #0000FF">end</span></span>
1771
1772   <span style="font-weight: bold"><span style="color: #0000FF">def</span></span> new
1773   <span style="font-weight: bold"><span style="color: #0000FF">end</span></span>
1774
1775   <span style="font-weight: bold"><span style="color: #0000FF">def</span></span> edit
1776   <span style="font-weight: bold"><span style="color: #0000FF">end</span></span>
1777
1778 <span style="font-weight: bold"><span style="color: #0000FF">end</span></span>
1779 </tt></pre></div></div>
1780 <div class="para"><p>You'll need to flesh this out with code to actually process requests appropriately in each method. Here's a version that (for simplicity's sake) only responds to requests that require HTML:</p></div>
1781 <div class="listingblock">
1782 <div class="content"><!-- Generator: GNU source-highlight 2.9
1783 by Lorenzo Bettini
1784 http://www.lorenzobettini.it
1785 http://www.gnu.org/software/src-highlite -->
1786 <pre><tt><span style="font-weight: bold"><span style="color: #0000FF">class</span></span> CommentsController <span style="color: #990000">&lt;</span> ApplicationController
1787   <span style="font-weight: bold"><span style="color: #0000FF">def</span></span> index
1788     <span style="color: #009900">@post</span> <span style="color: #990000">=</span> Post<span style="color: #990000">.</span>find<span style="color: #990000">(</span>params<span style="color: #990000">[:</span>post_id<span style="color: #990000">])</span>
1789     <span style="color: #009900">@comments</span> <span style="color: #990000">=</span> <span style="color: #009900">@post</span><span style="color: #990000">.</span>comments
1790   <span style="font-weight: bold"><span style="color: #0000FF">end</span></span>
1791
1792   <span style="font-weight: bold"><span style="color: #0000FF">def</span></span> show
1793     <span style="color: #009900">@post</span> <span style="color: #990000">=</span> Post<span style="color: #990000">.</span>find<span style="color: #990000">(</span>params<span style="color: #990000">[:</span>post_id<span style="color: #990000">])</span>
1794     <span style="color: #009900">@comment</span> <span style="color: #990000">=</span> Comment<span style="color: #990000">.</span>find<span style="color: #990000">(</span>params<span style="color: #990000">[:</span>id<span style="color: #990000">])</span>
1795   <span style="font-weight: bold"><span style="color: #0000FF">end</span></span>
1796
1797   <span style="font-weight: bold"><span style="color: #0000FF">def</span></span> new
1798     <span style="color: #009900">@post</span> <span style="color: #990000">=</span> Post<span style="color: #990000">.</span>find<span style="color: #990000">(</span>params<span style="color: #990000">[:</span>post_id<span style="color: #990000">])</span>
1799     <span style="color: #009900">@comment</span> <span style="color: #990000">=</span> <span style="color: #009900">@post</span><span style="color: #990000">.</span>comments<span style="color: #990000">.</span>build
1800   <span style="font-weight: bold"><span style="color: #0000FF">end</span></span>
1801
1802   <span style="font-weight: bold"><span style="color: #0000FF">def</span></span> create
1803     <span style="color: #009900">@post</span> <span style="color: #990000">=</span> Post<span style="color: #990000">.</span>find<span style="color: #990000">(</span>params<span style="color: #990000">[:</span>post_id<span style="color: #990000">])</span>
1804     <span style="color: #009900">@comment</span> <span style="color: #990000">=</span> <span style="color: #009900">@post</span><span style="color: #990000">.</span>comments<span style="color: #990000">.</span>build<span style="color: #990000">(</span>params<span style="color: #990000">[:</span>comment<span style="color: #990000">])</span>
1805     <span style="font-weight: bold"><span style="color: #0000FF">if</span></span> <span style="color: #009900">@comment</span><span style="color: #990000">.</span>save
1806       redirect_to post_comment_path<span style="color: #990000">(</span><span style="color: #009900">@post</span><span style="color: #990000">,</span> <span style="color: #009900">@comment</span><span style="color: #990000">)</span>
1807     <span style="font-weight: bold"><span style="color: #0000FF">else</span></span>
1808       render <span style="color: #990000">:</span>action <span style="color: #990000">=&gt;</span> <span style="color: #FF0000">"new"</span>
1809     <span style="font-weight: bold"><span style="color: #0000FF">end</span></span>
1810   <span style="font-weight: bold"><span style="color: #0000FF">end</span></span>
1811
1812   <span style="font-weight: bold"><span style="color: #0000FF">def</span></span> edit
1813     <span style="color: #009900">@post</span> <span style="color: #990000">=</span> Post<span style="color: #990000">.</span>find<span style="color: #990000">(</span>params<span style="color: #990000">[:</span>post_id<span style="color: #990000">])</span>
1814     <span style="color: #009900">@comment</span> <span style="color: #990000">=</span> Comment<span style="color: #990000">.</span>find<span style="color: #990000">(</span>params<span style="color: #990000">[:</span>id<span style="color: #990000">])</span>
1815   <span style="font-weight: bold"><span style="color: #0000FF">end</span></span>
1816
1817   <span style="font-weight: bold"><span style="color: #0000FF">def</span></span> update
1818     <span style="color: #009900">@post</span> <span style="color: #990000">=</span> Post<span style="color: #990000">.</span>find<span style="color: #990000">(</span>params<span style="color: #990000">[:</span>post_id<span style="color: #990000">])</span>
1819     <span style="color: #009900">@comment</span> <span style="color: #990000">=</span> Comment<span style="color: #990000">.</span>find<span style="color: #990000">(</span>params<span style="color: #990000">[:</span>id<span style="color: #990000">])</span>
1820     <span style="font-weight: bold"><span style="color: #0000FF">if</span></span> <span style="color: #009900">@comment</span><span style="color: #990000">.</span>update_attributes<span style="color: #990000">(</span>params<span style="color: #990000">[:</span>comment<span style="color: #990000">])</span>
1821       redirect_to post_comment_path<span style="color: #990000">(</span><span style="color: #009900">@post</span><span style="color: #990000">,</span> <span style="color: #009900">@comment</span><span style="color: #990000">)</span>
1822     <span style="font-weight: bold"><span style="color: #0000FF">else</span></span>
1823       render <span style="color: #990000">:</span>action <span style="color: #990000">=&gt;</span> <span style="color: #FF0000">"edit"</span>
1824     <span style="font-weight: bold"><span style="color: #0000FF">end</span></span>
1825   <span style="font-weight: bold"><span style="color: #0000FF">end</span></span>
1826
1827 <span style="font-weight: bold"><span style="color: #0000FF">end</span></span>
1828 </tt></pre></div></div>
1829 <div class="para"><p>You'll see a bit more complexity here than you did in the controller for posts. That's a side-effect of the nesting that you've set up; each request for a comment has to keep track of the post to which the comment is attached.</p></div>
1830 <div class="para"><p>In addition, the code takes advantage of some of the methods available for an association. For example, in the <tt>new</tt> method, it calls</p></div>
1831 <div class="listingblock">
1832 <div class="content"><!-- Generator: GNU source-highlight 2.9
1833 by Lorenzo Bettini
1834 http://www.lorenzobettini.it
1835 http://www.gnu.org/software/src-highlite -->
1836 <pre><tt><span style="color: #009900">@comment</span> <span style="color: #990000">=</span> <span style="color: #009900">@post</span><span style="color: #990000">.</span>comments<span style="color: #990000">.</span>build
1837 </tt></pre></div></div>
1838 <div class="para"><p>This creates a new <tt>Comment</tt> object <em>and</em> sets up the <tt>post_id</tt> field to have the <tt>id</tt> from the specified <tt>Post</tt> object in a single operation.</p></div>
1839 <h3 id="_building_views">8.5. Building Views</h3>
1840 <div class="para"><p>Because you skipped scaffolding, you'll need to build views for comments "by hand." Invoking <tt>script/generate controller</tt> will give you skeleton views, but they'll be devoid of actual content. Here's a first pass at fleshing out the comment views.</p></div>
1841 <div class="para"><p>The <tt>index.html.erb</tt> view:</p></div>
1842 <div class="listingblock">
1843 <div class="content"><!-- Generator: GNU source-highlight 2.9
1844 by Lorenzo Bettini
1845 http://www.lorenzobettini.it
1846 http://www.gnu.org/software/src-highlite -->
1847 <pre><tt><span style="color: #FF0000">&lt;h1&gt;</span>Comments <span style="font-weight: bold"><span style="color: #0000FF">for</span></span> <span style="color: #FF0000">&lt;%= @post.title %&gt;&lt;/h1&gt;</span>
1848
1849 <span style="color: #FF0000">&lt;table&gt;</span>
1850   <span style="color: #FF0000">&lt;tr&gt;</span>
1851     <span style="color: #FF0000">&lt;th&gt;</span>Commenter<span style="color: #FF0000">&lt;/th&gt;</span>
1852     <span style="color: #FF0000">&lt;th&gt;</span>Body<span style="color: #FF0000">&lt;/th&gt;</span>
1853   <span style="color: #FF0000">&lt;/tr&gt;</span>
1854
1855 <span style="color: #FF0000">&lt;% for comment in @comments %&gt;</span>
1856   <span style="color: #FF0000">&lt;tr&gt;</span>
1857     <span style="color: #FF0000">&lt;td&gt;&lt;%=h comment.commenter %&gt;&lt;/td&gt;</span>
1858     <span style="color: #FF0000">&lt;td&gt;&lt;%=h comment.body %&gt;&lt;/td&gt;</span>
1859     <span style="color: #FF0000">&lt;td&gt;&lt;%= link_to 'Show', post_comment_path(@post, comment) %&gt;&lt;/td&gt;</span>
1860     <span style="color: #FF0000">&lt;td&gt;&lt;%= link_to 'Edit', edit_post_comment_path(@post, comment) %&gt;&lt;/td&gt;</span>
1861     <span style="color: #FF0000">&lt;td&gt;&lt;%= link_to 'Destroy', post_comment_path(@post, comment), :confirm =&gt;</span> <span style="color: #FF0000">'Are you sure?'</span><span style="color: #990000">,</span> <span style="color: #990000">:</span>method <span style="color: #990000">=&gt;</span> <span style="color: #990000">:</span>delete <span style="color: #990000">%&gt;</span><span style="color: #FF0000">&lt;/td&gt;</span>
1862   <span style="color: #FF0000">&lt;/tr&gt;</span>
1863 <span style="color: #FF0000">&lt;% end %&gt;</span>
1864 <span style="color: #FF0000">&lt;/table&gt;</span>
1865
1866 <span style="color: #FF0000">&lt;br /&gt;</span>
1867
1868 <span style="color: #FF0000">&lt;%= link_to 'New comment', new_post_comment_path(@post) %&gt;</span>
1869 <span style="color: #FF0000">&lt;%= link_to 'Back to Post', @post %&gt;</span>
1870 </tt></pre></div></div>
1871 <div class="para"><p>The <tt>new.html.erb</tt> view:</p></div>
1872 <div class="listingblock">
1873 <div class="content"><!-- Generator: GNU source-highlight 2.9
1874 by Lorenzo Bettini
1875 http://www.lorenzobettini.it
1876 http://www.gnu.org/software/src-highlite -->
1877 <pre><tt><span style="color: #FF0000">&lt;h1&gt;</span>New comment<span style="color: #FF0000">&lt;/h1&gt;</span>
1878
1879 <span style="color: #FF0000">&lt;% form_for([@post, @comment]) do |f| %&gt;</span>
1880   <span style="color: #FF0000">&lt;%= f.error_messages %&gt;</span>
1881
1882   <span style="color: #FF0000">&lt;p&gt;</span>
1883     <span style="color: #FF0000">&lt;%= f.label :commenter %&gt;&lt;br /&gt;</span>
1884     <span style="color: #FF0000">&lt;%= f.text_field :commenter %&gt;</span>
1885   <span style="color: #FF0000">&lt;/p&gt;</span>
1886   <span style="color: #FF0000">&lt;p&gt;</span>
1887     <span style="color: #FF0000">&lt;%= f.label :body %&gt;&lt;br /&gt;</span>
1888     <span style="color: #FF0000">&lt;%= f.text_area :body %&gt;</span>
1889   <span style="color: #FF0000">&lt;/p&gt;</span>
1890   <span style="color: #FF0000">&lt;p&gt;</span>
1891     <span style="color: #FF0000">&lt;%= f.submit "Create" %&gt;</span>
1892   <span style="color: #FF0000">&lt;/p&gt;</span>
1893 <span style="color: #FF0000">&lt;% end %&gt;</span>
1894
1895 <span style="color: #FF0000">&lt;%= link_to 'Back', post_comments_path(@post) %&gt;</span>
1896 </tt></pre></div></div>
1897 <div class="para"><p>The <tt>show.html.erb</tt> view:</p></div>
1898 <div class="listingblock">
1899 <div class="content"><!-- Generator: GNU source-highlight 2.9
1900 by Lorenzo Bettini
1901 http://www.lorenzobettini.it
1902 http://www.gnu.org/software/src-highlite -->
1903 <pre><tt><span style="color: #FF0000">&lt;h1&gt;</span>Comment on <span style="color: #FF0000">&lt;%= @post.title %&gt;&lt;/h1&gt;</span>
1904
1905 <span style="color: #FF0000">&lt;p&gt;</span>
1906   <span style="color: #FF0000">&lt;b&gt;</span>Commenter<span style="color: #990000">:</span><span style="color: #FF0000">&lt;/b&gt;</span>
1907   <span style="color: #FF0000">&lt;%=h @comment.commenter %&gt;</span>
1908 <span style="color: #FF0000">&lt;/p&gt;</span>
1909
1910 <span style="color: #FF0000">&lt;p&gt;</span>
1911   <span style="color: #FF0000">&lt;b&gt;</span>Comment<span style="color: #990000">:</span><span style="color: #FF0000">&lt;/b&gt;</span>
1912   <span style="color: #FF0000">&lt;%=h @comment.body %&gt;</span>
1913 <span style="color: #FF0000">&lt;/p&gt;</span>
1914
1915 <span style="color: #FF0000">&lt;%= link_to 'Edit', edit_post_comment_path(@post, @comment) %&gt;</span> <span style="color: #990000">|</span>
1916 <span style="color: #FF0000">&lt;%= link_to 'Back', post_comments_path(@post) %&gt;</span>
1917 </tt></pre></div></div>
1918 <div class="para"><p>The <tt>edit.html.erb</tt> view:</p></div>
1919 <div class="listingblock">
1920 <div class="content"><!-- Generator: GNU source-highlight 2.9
1921 by Lorenzo Bettini
1922 http://www.lorenzobettini.it
1923 http://www.gnu.org/software/src-highlite -->
1924 <pre><tt><span style="color: #FF0000">&lt;h1&gt;</span>Editing comment<span style="color: #FF0000">&lt;/h1&gt;</span>
1925
1926 <span style="color: #FF0000">&lt;% form_for([@post, @comment]) do |f| %&gt;</span>
1927   <span style="color: #FF0000">&lt;%= f.error_messages %&gt;</span>
1928
1929   <span style="color: #FF0000">&lt;p&gt;</span>
1930     <span style="color: #FF0000">&lt;%= f.label :commenter %&gt;&lt;br /&gt;</span>
1931     <span style="color: #FF0000">&lt;%= f.text_field :commenter %&gt;</span>
1932   <span style="color: #FF0000">&lt;/p&gt;</span>
1933   <span style="color: #FF0000">&lt;p&gt;</span>
1934     <span style="color: #FF0000">&lt;%= f.label :body %&gt;&lt;br /&gt;</span>
1935     <span style="color: #FF0000">&lt;%= f.text_area :body %&gt;</span>
1936   <span style="color: #FF0000">&lt;/p&gt;</span>
1937   <span style="color: #FF0000">&lt;p&gt;</span>
1938     <span style="color: #FF0000">&lt;%= f.submit "Update" %&gt;</span>
1939   <span style="color: #FF0000">&lt;/p&gt;</span>
1940 <span style="color: #FF0000">&lt;% end %&gt;</span>
1941
1942 <span style="color: #FF0000">&lt;%= link_to 'Show', post_comment_path(@post, @comment) %&gt;</span> <span style="color: #990000">|</span>
1943 <span style="color: #FF0000">&lt;%= link_to 'Back', post_comments_path(@post) %&gt;</span>
1944 </tt></pre></div></div>
1945 <div class="para"><p>Again, the added complexity here (compared to the views you saw for managing comments) comes from the necessity of juggling a post and its comments at the same time.</p></div>
1946 <h3 id="_hooking_comments_to_posts">8.6. Hooking Comments to Posts</h3>
1947 <div class="para"><p>As a final step, I'll modify the <tt>show.html.erb</tt> view for a post to show the comments on that post, and to allow managing those comments:</p></div>
1948 <div class="listingblock">
1949 <div class="content"><!-- Generator: GNU source-highlight 2.9
1950 by Lorenzo Bettini
1951 http://www.lorenzobettini.it
1952 http://www.gnu.org/software/src-highlite -->
1953 <pre><tt><span style="color: #FF0000">&lt;p&gt;</span>
1954   <span style="color: #FF0000">&lt;b&gt;</span>Name<span style="color: #990000">:</span><span style="color: #FF0000">&lt;/b&gt;</span>
1955   <span style="color: #FF0000">&lt;%=h @post.name %&gt;</span>
1956 <span style="color: #FF0000">&lt;/p&gt;</span>
1957
1958 <span style="color: #FF0000">&lt;p&gt;</span>
1959   <span style="color: #FF0000">&lt;b&gt;</span>Title<span style="color: #990000">:</span><span style="color: #FF0000">&lt;/b&gt;</span>
1960   <span style="color: #FF0000">&lt;%=h @post.title %&gt;</span>
1961 <span style="color: #FF0000">&lt;/p&gt;</span>
1962
1963 <span style="color: #FF0000">&lt;p&gt;</span>
1964   <span style="color: #FF0000">&lt;b&gt;</span>Content<span style="color: #990000">:</span><span style="color: #FF0000">&lt;/b&gt;</span>
1965   <span style="color: #FF0000">&lt;%=h @post.content %&gt;</span>
1966 <span style="color: #FF0000">&lt;/p&gt;</span>
1967
1968 <span style="color: #FF0000">&lt;h2&gt;</span>Comments<span style="color: #FF0000">&lt;/h2&gt;</span>
1969 <span style="color: #FF0000">&lt;% @post.comments.each do |c| %&gt;</span>
1970         <span style="color: #FF0000">&lt;p&gt;</span>
1971           <span style="color: #FF0000">&lt;b&gt;</span>Commenter<span style="color: #990000">:</span><span style="color: #FF0000">&lt;/b&gt;</span>
1972           <span style="color: #FF0000">&lt;%=h c.commenter %&gt;</span>
1973         <span style="color: #FF0000">&lt;/p&gt;</span>
1974
1975         <span style="color: #FF0000">&lt;p&gt;</span>
1976           <span style="color: #FF0000">&lt;b&gt;</span>Comment<span style="color: #990000">:</span><span style="color: #FF0000">&lt;/b&gt;</span>
1977           <span style="color: #FF0000">&lt;%=h c.body %&gt;</span>
1978         <span style="color: #FF0000">&lt;/p&gt;</span>
1979 <span style="color: #FF0000">&lt;% end %&gt;</span>
1980
1981 <span style="color: #FF0000">&lt;%= link_to 'Edit', edit_post_path(@post) %&gt;</span> <span style="color: #990000">|</span>
1982 <span style="color: #FF0000">&lt;%= link_to 'Back', posts_path %&gt;</span>
1983 <span style="color: #FF0000">&lt;%= link_to 'Manage Comments', post_comments_path(@post) %&gt;</span>
1984 </tt></pre></div></div>
1985 <div class="para"><p>Note that each post has its own individual comments collection, accessible as <tt>@post.comments</tt>. That's a consequence of the declarative associations in the models. Path helpers such as <tt>post_comments_path</tt> come from the nested route declaration in <tt>config/routes.rb</tt>.</p></div>
1986 </div>
1987 <h2 id="_what_s_next">9. What's Next?</h2>
1988 <div class="sectionbody">
1989 <div class="para"><p>Now that you've seen your first Rails application, you should feel free to update it and experiment on your own. But you don't have to do everything without help. As you need assistance getting up and running with Rails, feel free to consult these support resources:</p></div>
1990 <div class="ilist"><ul>
1991 <li>
1992 <p>
1993 The <a href="http://manuals.rubyonrails.org/">Ruby On Rails guides</a>
1994 </p>
1995 </li>
1996 <li>
1997 <p>
1998 The <a href="http://groups.google.com/group/rubyonrails-talk">Ruby on Rails mailing list</a>
1999 </p>
2000 </li>
2001 <li>
2002 <p>
2003 The #rubyonrails channel on irc.freenode.net
2004 </p>
2005 </li>
2006 <li>
2007 <p>
2008 The <a href="http://wiki.rubyonrails.org/rails">Rails wiki</a>
2009 </p>
2010 </li>
2011 </ul></div>
2012 <div class="para"><p>Rails also comes with built-in help that you can generate using the rake command-line utility:</p></div>
2013 <div class="ilist"><ul>
2014 <li>
2015 <p>
2016 Running <tt>rake doc:guides</tt> will put a full copy of the Rails Guides in the <tt>/doc/guides</tt> folder of your application. Open <tt>/doc/guides/index.html</tt> in your web browser to explore the Guides.
2017 </p>
2018 </li>
2019 <li>
2020 <p>
2021 Running <tt>rake doc:rails</tt> will put a full copy of the API documentation for Rails in the <tt>/doc/api</tt> folder of your application. Open <tt>/doc/api/index.html</tt> in your web browser to explore the API documentation.
2022 </p>
2023 </li>
2024 </ul></div>
2025 </div>
2026 <h2 id="_changelog">10. Changelog</h2>
2027 <div class="sectionbody">
2028 <div class="para"><p><a href="http://rails.lighthouseapp.com/projects/16213-rails-guides/tickets/2">Lighthouse ticket</a></p></div>
2029 <div class="ilist"><ul>
2030 <li>
2031 <p>
2032 November 3, 2008: Formatting patch from Dave Rothlisberger
2033 </p>
2034 </li>
2035 <li>
2036 <p>
2037 November 1, 2008: First approved version by <a href="../authors.html#mgunderloy">Mike Gunderloy</a>
2038 </p>
2039 </li>
2040 <li>
2041 <p>
2042 October 16, 2008: Revised based on feedback from Pratik Naik by <a href="../authors.html#mgunderloy">Mike Gunderloy</a> (not yet approved for publication)
2043 </p>
2044 </li>
2045 <li>
2046 <p>
2047 October 13, 2008: First complete draft by <a href="../authors.html#mgunderloy">Mike Gunderloy</a> (not yet approved for publication)
2048 </p>
2049 </li>
2050 <li>
2051 <p>
2052 October 12, 2008: More detail, rearrangement, editing by <a href="../authors.html#mgunderloy">Mike Gunderloy</a> (not yet approved for publication)
2053 </p>
2054 </li>
2055 <li>
2056 <p>
2057 September 8, 2008: initial version by James Miller (not yet approved for publication)
2058 </p>
2059 </li>
2060 </ul></div>
2061 </div>
2062
2063                 </div>
2064         </div>
2065 </body>
2066 </html>