1 files changed, 60 insertions, 9 deletions

diff --git a/actionpack/lib/action_dispatch/routing/mapper.rb b/actionpack/lib/action_dispatch/routing/mapper.rb
index b52f66faf1..ddb34a2394 100644
--- a/actionpack/lib/action_dispatch/routing/mapper.rb
+++ b/actionpack/lib/action_dispatch/routing/mapper.rb
@@ -1585,7 +1585,7 @@ module ActionDispatch
           end
       end
 
-      # Routing Concerns allows you to declare common routes that can be reused
+      # Routing Concerns allow you to declare common routes that can be reused
       # inside others resources and routes.
       #
       #   concern :commentable do
@@ -1608,13 +1608,63 @@ module ActionDispatch
       module Concerns
         # Define a routing concern using a name.
         #
-        #   concern :commentable do
-        #     resources :comments
+        # Concerns may be defined inline, using a block, or handled by
+        # another object, by passing that object as the second parameter.
+        #
+        # The concern object, if supplied, should respond to <tt>call</tt>,
+        # which will receive two parameters:
+        #
+        #   * The current mapper
+        #   * A hash of options which the concern object may use
+        #
+        # Options may also be used by concerns defined in a block by accepting
+        # a block parameter. So, using a block, you might do something as
+        # simple as limit the actions available on certain resources, passing
+        # standard resource options through the concern:
+        #
+        #   concern :commentable do |options|
+        #     resources :comments, options
         #   end
         #
-        # Any routing helpers can be used inside a concern.
-        def concern(name, &block)
-          @concerns[name] = block
+        #   resources :posts, concerns: :commentable
+        #   resources :archived_posts do
+        #     # Don't allow comments on archived posts
+        #     concerns :commentable, only: [:index, :show]
+        #   end
+        #
+        # Or, using a callable object, you might implement something more
+        # specific to your application, which would be out of place in your
+        # routes file.
+        #
+        #   # purchasable.rb
+        #   class Purchasable
+        #     def initialize(defaults = {})
+        #       @defaults = defaults
+        #     end
+        #
+        #     def call(mapper, options = {})
+        #       options = @defaults.merge(options)
+        #       mapper.resources :purchases
+        #       mapper.resources :receipts
+        #       mapper.resources :returns if options[:returnable]
+        #     end
+        #   end
+        #
+        #   # routes.rb
+        #   concern :purchasable, Purchasable.new(returnable: true)
+        #
+        #   resources :toys, concerns: :purchasable
+        #   resources :electronics, concerns: :purchasable
+        #   resources :pets do
+        #     concerns :purchasable, returnable: false
+        #   end
+        #
+        # Any routing helpers can be used inside a concern. If using a
+        # callable, they're accessible from the Mapper that's passed to
+        # <tt>call</tt>.
+        def concern(name, callable = nil, &block)
+          callable ||= lambda { |mapper, options| mapper.instance_exec(options, &block) }
+          @concerns[name] = callable
         end
 
         # Use the named concerns
@@ -1628,10 +1678,11 @@ module ActionDispatch
         #   namespace :posts do
         #     concerns :commentable
         #   end
-        def concerns(*names)
-          names.flatten.each do |name|
+        def concerns(*args)
+          options = args.extract_options!
+          args.flatten.each do |name|
             if concern = @concerns[name]
-              instance_eval(&concern)
+              concern.call(self, options)
             else
               raise ArgumentError, "No concern named #{name} was found!"
             end