vendor/rails/actionpack/lib/action_controller/helpers.rb

   1 # FIXME: helper { ... } is broken on Ruby 1.9
   2 module ActionController #:nodoc:
   3   module Helpers #:nodoc:
   4     HELPERS_DIR = (defined?(RAILS_ROOT) ? "#{RAILS_ROOT}/app/helpers" : "app/helpers")
   5
   6     def self.included(base)
   7       # Initialize the base module to aggregate its helpers.
   8       base.class_inheritable_accessor :master_helper_module
   9       base.master_helper_module = Module.new
  10
  11       # Extend base with class methods to declare helpers.
  12       base.extend(ClassMethods)
  13
  14       base.class_eval do
  15         # Wrap inherited to create a new master helper module for subclasses.
  16         class << self
  17           alias_method_chain :inherited, :helper
  18         end
  19       end
  20     end
  21
  22     # The Rails framework provides a large number of helpers for working with +assets+, +dates+, +forms+,
  23     # +numbers+ and Active Record objects, to name a few. These helpers are available to all templates
  24     # by default.
  25     #
  26     # In addition to using the standard template helpers provided in the Rails framework, creating custom helpers to
  27     # extract complicated logic or reusable functionality is strongly encouraged.  By default, the controller will
  28     # include a helper whose name matches that of the controller, e.g., <tt>MyController</tt> will automatically
  29     # include <tt>MyHelper</tt>.
  30     #
  31     # Additional helpers can be specified using the +helper+ class method in <tt>ActionController::Base</tt> or any
  32     # controller which inherits from it.
  33     #
  34     # ==== Examples
  35     # The +to_s+ method from the Time class can be wrapped in a helper method to display a custom message if
  36     # the Time object is blank:
  37     #
  38     #   module FormattedTimeHelper
  39     #     def format_time(time, format=:long, blank_message="&nbsp;")
  40     #       time.blank? ? blank_message : time.to_s(format)
  41     #     end
  42     #   end
  43     #
  44     # FormattedTimeHelper can now be included in a controller, using the +helper+ class method:
  45     #
  46     #   class EventsController < ActionController::Base
  47     #     helper FormattedTimeHelper
  48     #     def index
  49     #       @events = Event.find(:all)
  50     #     end
  51     #   end
  52     #
  53     # Then, in any view rendered by <tt>EventController</tt>, the <tt>format_time</tt> method can be called:
  54     #
  55     #   <% @events.each do |event| -%>
  56     #     <p>
  57     #       <% format_time(event.time, :short, "N/A") %> | <%= event.name %>
  58     #     </p>
  59     #   <% end -%>
  60     #
  61     # Finally, assuming we have two event instances, one which has a time and one which does not,
  62     # the output might look like this:
  63     #
  64     #   23 Aug 11:30 | Carolina Railhawks Soccer Match
  65     #   N/A | Carolina Railhaws Training Workshop
  66     #
  67     module ClassMethods
  68       # Makes all the (instance) methods in the helper module available to templates rendered through this controller.
  69       # See ActionView::Helpers (link:classes/ActionView/Helpers.html) for more about making your own helper modules
  70       # available to the templates.
  71       def add_template_helper(helper_module) #:nodoc:
  72         master_helper_module.module_eval { include helper_module }
  73       end
  74
  75       # The +helper+ class method can take a series of helper module names, a block, or both.
  76       #
  77       # * <tt>*args</tt>: One or more modules, strings or symbols, or the special symbol <tt>:all</tt>.
  78       # * <tt>&block</tt>: A block defining helper methods.
  79       #
  80       # ==== Examples
  81       # When the argument is a string or symbol, the method will provide the "_helper" suffix, require the file
  82       # and include the module in the template class.  The second form illustrates how to include custom helpers
  83       # when working with namespaced controllers, or other cases where the file containing the helper definition is not
  84       # in one of Rails' standard load paths:
  85       #   helper :foo             # => requires 'foo_helper' and includes FooHelper
  86       #   helper 'resources/foo'  # => requires 'resources/foo_helper' and includes Resources::FooHelper
  87       #
  88       # When the argument is a module it will be included directly in the template class.
  89       #   helper FooHelper # => includes FooHelper
  90       #
  91       # When the argument is the symbol <tt>:all</tt>, the controller will include all helpers from
  92       # <tt>app/helpers/**/*.rb</tt> under RAILS_ROOT.
  93       #   helper :all
  94       #
  95       # Additionally, the +helper+ class method can receive and evaluate a block, making the methods defined available
  96       # to the template.
  97       #   # One line
  98       #   helper { def hello() "Hello, world!" end }
  99       #   # Multi-line
 100       #   helper do
 101       #     def foo(bar)
 102       #       "#{bar} is the very best"
 103       #     end
 104       #   end
 105       #
 106       # Finally, all the above styles can be mixed together, and the +helper+ method can be invoked with a mix of
 107       # +symbols+, +strings+, +modules+ and blocks.
 108       #   helper(:three, BlindHelper) { def mice() 'mice' end }
 109       #
 110       def helper(*args, &block)
 111         args.flatten.each do |arg|
 112           case arg
 113             when Module
 114               add_template_helper(arg)
 115             when :all
 116               helper(all_application_helpers)
 117             when String, Symbol
 118               file_name  = arg.to_s.underscore + '_helper'
 119               class_name = file_name.camelize
 120
 121               begin
 122                 require_dependency(file_name)
 123               rescue LoadError => load_error
 124                 requiree = / -- (.*?)(\.rb)?$/.match(load_error.message).to_a[1]
 125                 if requiree == file_name
 126                   msg = "Missing helper file helpers/#{file_name}.rb"
 127                   raise LoadError.new(msg).copy_blame!(load_error)
 128                 else
 129                   raise
 130                 end
 131               end
 132
 133               add_template_helper(class_name.constantize)
 134             else
 135               raise ArgumentError, "helper expects String, Symbol, or Module argument (was: #{args.inspect})"
 136           end
 137         end
 138
 139         # Evaluate block in template class if given.
 140         master_helper_module.module_eval(&block) if block_given?
 141       end
 142
 143       # Declare a controller method as a helper. For example, the following
 144       # makes the +current_user+ controller method available to the view:
 145       #   class ApplicationController < ActionController::Base
 146       #     helper_method :current_user, :logged_in?
 147       #
 148       #     def current_user
 149       #       @current_user ||= User.find_by_id(session[:user])
 150       #     end
 151       #
 152       #      def logged_in?
 153       #        current_user != nil
 154       #      end
 155       #   end
 156       #
 157       # In a view:
 158       #  <% if logged_in? -%>Welcome, <%= current_user.name %><% end -%>
 159       def helper_method(*methods)
 160         methods.flatten.each do |method|
 161           master_helper_module.module_eval <<-end_eval
 162             def #{method}(*args, &block)
 163               controller.send(%(#{method}), *args, &block)
 164             end
 165           end_eval
 166         end
 167       end
 168
 169       # Declares helper accessors for controller attributes. For example, the
 170       # following adds new +name+ and <tt>name=</tt> instance methods to a
 171       # controller and makes them available to the view:
 172       #   helper_attr :name
 173       #   attr_accessor :name
 174       def helper_attr(*attrs)
 175         attrs.flatten.each { |attr| helper_method(attr, "#{attr}=") }
 176       end
 177
 178       # Provides a proxy to access helpers methods from outside the view.
 179       def helpers
 180         unless @helper_proxy
 181           @helper_proxy = ActionView::Base.new
 182           @helper_proxy.extend master_helper_module
 183         else
 184           @helper_proxy
 185         end
 186       end
 187
 188       private
 189         def default_helper_module!
 190           unless name.blank?
 191             module_name = name.sub(/Controller$|$/, 'Helper')
 192             module_path = module_name.split('::').map { |m| m.underscore }.join('/')
 193             require_dependency module_path
 194             helper module_name.constantize
 195           end
 196         rescue MissingSourceFile => e
 197           raise unless e.is_missing? module_path
 198         rescue NameError => e
 199           raise unless e.missing_name? module_name
 200         end
 201
 202         def inherited_with_helper(child)
 203           inherited_without_helper(child)
 204
 205           begin
 206             child.master_helper_module = Module.new
 207             child.master_helper_module.__send__ :include, master_helper_module
 208             child.__send__ :default_helper_module!
 209           rescue MissingSourceFile => e
 210             raise unless e.is_missing?("helpers/#{child.controller_path}_helper")
 211           end
 212         end
 213
 214         # Extract helper names from files in app/helpers/**/*.rb
 215         def all_application_helpers
 216           extract = /^#{Regexp.quote(HELPERS_DIR)}\/?(.*)_helper.rb$/
 217           Dir["#{HELPERS_DIR}/**/*_helper.rb"].map { |file| file.sub extract, '\1' }
 218         end
 219     end
 220   end
 221 end