--- /dev/null
+== Add an `acts_as_yaffle` method to Active Record ==
+
+A common pattern in plugins is to add a method called 'acts_as_something' to models. In this case, you want to write a method called 'acts_as_yaffle' that adds a 'squawk' method to your models.
+
+To begin, set up your files so that you have:
+
+*vendor/plugins/yaffle/test/acts_as_yaffle_test.rb*
+
+[source, ruby]
+------------------------------------------------------
+require File.dirname(__FILE__) + '/test_helper.rb'
+
+class ActsAsYaffleTest < Test::Unit::TestCase
+end
+------------------------------------------------------
+
+*vendor/plugins/yaffle/lib/yaffle.rb*
+
+[source, ruby]
+------------------------------------------------------
+require 'yaffle/acts_as_yaffle'
+------------------------------------------------------
+
+*vendor/plugins/yaffle/lib/yaffle/acts_as_yaffle.rb*
+
+[source, ruby]
+------------------------------------------------------
+module Yaffle
+ # your code will go here
+end
+------------------------------------------------------
+
+Note that after requiring 'acts_as_yaffle' you also have to include it into ActiveRecord::Base so that your plugin methods will be available to the rails models.
+
+One of the most common plugin patterns for 'acts_as_yaffle' plugins is to structure your file like so:
+
+*vendor/plugins/yaffle/lib/yaffle/acts_as_yaffle.rb*
+
+[source, ruby]
+------------------------------------------------------
+module Yaffle
+ def self.included(base)
+ base.send :extend, ClassMethods
+ end
+
+ module ClassMethods
+ # any method placed here will apply to classes, like Hickwall
+ def acts_as_something
+ send :include, InstanceMethods
+ end
+ end
+
+ module InstanceMethods
+ # any method placed here will apply to instaces, like @hickwall
+ end
+end
+------------------------------------------------------
+
+With structure you can easily separate the methods that will be used for the class (like `Hickwall.some_method`) and the instance (like `@hickwell.some_method`).
+
+=== Add a class method ===
+
+This plugin will expect that you've added a method to your model named 'last_squawk'. However, the plugin users might have already defined a method on their model named 'last_squawk' that they use for something else. This plugin will allow the name to be changed by adding a class method called 'yaffle_text_field'.
+
+To start out, write a failing test that shows the behavior you'd like:
+
+*vendor/plugins/yaffle/test/acts_as_yaffle_test.rb*
+
+[source, ruby]
+------------------------------------------------------
+require File.dirname(__FILE__) + '/test_helper.rb'
+
+class Hickwall < ActiveRecord::Base
+ acts_as_yaffle
+end
+
+class Wickwall < ActiveRecord::Base
+ acts_as_yaffle :yaffle_text_field => :last_tweet
+end
+
+class ActsAsYaffleTest < Test::Unit::TestCase
+ load_schema
+
+ def test_a_hickwalls_yaffle_text_field_should_be_last_squawk
+ assert_equal "last_squawk", Hickwall.yaffle_text_field
+ end
+
+ def test_a_wickwalls_yaffle_text_field_should_be_last_tweet
+ assert_equal "last_tweet", Wickwall.yaffle_text_field
+ end
+end
+------------------------------------------------------
+
+To make these tests pass, you could modify your `acts_as_yaffle` file like so:
+
+*vendor/plugins/yaffle/lib/yaffle/acts_as_yaffle.rb*
+
+[source, ruby]
+------------------------------------------------------
+module Yaffle
+ def self.included(base)
+ base.send :extend, ClassMethods
+ end
+
+ module ClassMethods
+ def acts_as_yaffle(options = {})
+ cattr_accessor :yaffle_text_field
+ self.yaffle_text_field = (options[:yaffle_text_field] || :last_squawk).to_s
+ end
+ end
+end
+
+ActiveRecord::Base.send :include, Yaffle
+------------------------------------------------------
+
+=== Add an instance method ===
+
+This plugin will add a method named 'squawk' to any Active Record objects that call 'acts_as_yaffle'. The 'squawk' method will simply set the value of one of the fields in the database.
+
+To start out, write a failing test that shows the behavior you'd like:
+
+*vendor/plugins/yaffle/test/acts_as_yaffle_test.rb*
+
+[source, ruby]
+------------------------------------------------------
+require File.dirname(__FILE__) + '/test_helper.rb'
+
+class Hickwall < ActiveRecord::Base
+ acts_as_yaffle
+end
+
+class Wickwall < ActiveRecord::Base
+ acts_as_yaffle :yaffle_text_field => :last_tweet
+end
+
+class ActsAsYaffleTest < Test::Unit::TestCase
+ load_schema
+
+ def test_a_hickwalls_yaffle_text_field_should_be_last_squawk
+ assert_equal "last_squawk", Hickwall.yaffle_text_field
+ end
+
+ def test_a_wickwalls_yaffle_text_field_should_be_last_tweet
+ assert_equal "last_tweet", Wickwall.yaffle_text_field
+ end
+
+ def test_hickwalls_squawk_should_populate_last_squawk
+ hickwall = Hickwall.new
+ hickwall.squawk("Hello World")
+ assert_equal "squawk! Hello World", hickwall.last_squawk
+ end
+
+ def test_wickwalls_squawk_should_populate_last_tweeted_at
+ wickwall = Wickwall.new
+ wickwall.squawk("Hello World")
+ assert_equal "squawk! Hello World", wickwall.last_tweet
+ end
+end
+------------------------------------------------------
+
+Run this test to make sure the last two tests fail, then update 'acts_as_yaffle.rb' to look like this:
+
+*vendor/plugins/yaffle/lib/yaffle/acts_as_yaffle.rb*
+
+[source, ruby]
+------------------------------------------------------
+module Yaffle
+ def self.included(base)
+ base.send :extend, ClassMethods
+ end
+
+ module ClassMethods
+ def acts_as_yaffle(options = {})
+ cattr_accessor :yaffle_text_field
+ self.yaffle_text_field = (options[:yaffle_text_field] || :last_squawk).to_s
+ send :include, InstanceMethods
+ end
+ end
+
+ module InstanceMethods
+ def squawk(string)
+ write_attribute(self.class.yaffle_text_field, string.to_squawk)
+ end
+ end
+end
+
+ActiveRecord::Base.send :include, Yaffle
+------------------------------------------------------
+
+.Editor's note:
+NOTE: The use of `write_attribute` to write to the field in model is just one example of how a plugin can interact with the model, and will not always be the right method to use. For example, you could also use `send("#{self.class.yaffle_text_field}=", string.to_squawk)`.
projects / depot.git / blobdiff