1 files changed, 56 insertions, 7 deletions

diff --git a/actionpack/lib/action_controller/metal.rb b/actionpack/lib/action_controller/metal.rb
index 329798e84f..e5db31061b 100644
--- a/actionpack/lib/action_controller/metal.rb
+++ b/actionpack/lib/action_controller/metal.rb
@@ -36,19 +36,68 @@ module ActionController
       action = action.to_s
       raise "MiddlewareStack#build requires an app" unless app
 
-      reverse.inject(app) do |a, middleware|
+      middlewares.reverse.inject(app) do |a, middleware|
         middleware.valid?(action) ?
           middleware.build(a) : a
       end
     end
   end
 
-  # Provides a way to get a valid Rack application from a controller.
+  # <tt>ActionController::Metal</tt> is the simplest possible controller, providing a
+  # valid Rack interface without the additional niceties provided by
+  # <tt>ActionController::Base</tt>.
+  #
+  # A sample metal controller might look like this:
+  #
+  #   class HelloController < ActionController::Metal
+  #     def index
+  #       self.response_body = "Hello World!"
+  #     end
+  #   end
+  #
+  # And then to route requests to your metal controller, you would add
+  # something like this to <tt>config/routes.rb</tt>:
+  #
+  #   match 'hello', :to => HelloController.action(:index)
+  #
+  # The +action+ method returns a valid Rack application for the \Rails
+  # router to dispatch to.
+  #
+  # == Rendering Helpers
+  #
+  # <tt>ActionController::Metal</tt> by default provides no utilities for rendering
+  # views, partials, or other responses aside from explicitly calling of
+  # <tt>response_body=</tt>, <tt>content_type=</tt>, and <tt>status=</tt>. To
+  # add the render helpers you're used to having in a normal controller, you
+  # can do the following:
+  #
+  #   class HelloController < ActionController::Metal
+  #     include ActionController::Rendering
+  #     append_view_path "#{Rails.root}/app/views"
+  #
+  #     def index
+  #       render "hello/index"
+  #     end
+  #   end
+  #
+  # == Redirection Helpers
+  #
+  # To add redirection helpers to your metal controller, do the following:
+  #
+  #   class HelloController < ActionController::Metal
+  #     include ActionController::Redirecting
+  #     include Rails.application.routes.url_helpers
+  #
+  #     def index
+  #       redirect_to root_url
+  #     end
+  #   end
+  #
+  # == Other Helpers
+  #
+  # You can refer to the modules included in <tt>ActionController::Base</tt> to see
+  # other features you can bring into your metal controller.
   #
-  # In AbstractController, dispatching is triggered directly by calling #process on a new controller.
-  # <tt>ActionController::Metal</tt> provides an <tt>action</tt> method that returns a valid Rack application for a
-  # given action. Other rack builders, such as Rack::Builder, Rack::URLMap, and the \Rails router,
-  # can dispatch directly to actions returned by controllers in your application.
   class Metal < AbstractController::Base
     abstract!
 
@@ -133,7 +182,7 @@ module ActionController
     end
 
     def response_body=(val)
-      body = val.respond_to?(:each) ? val : [val]
+      body = val.nil? ? nil : (val.respond_to?(:each) ? val : [val])
       super body
     end