Add Request#formats=(extensions) that lets you set multiple formats directly in a prioritized order

1 files changed, 21 insertions, 0 deletions

diff --git a/actionpack/lib/action_dispatch/http/mime_negotiation.rb b/actionpack/lib/action_dispatch/http/mime_negotiation.rb
index e31f3b823d..0f98e84788 100644
--- a/actionpack/lib/action_dispatch/http/mime_negotiation.rb
+++ b/actionpack/lib/action_dispatch/http/mime_negotiation.rb
@@ -80,6 +80,27 @@ module ActionDispatch
         @env["action_dispatch.request.formats"] = [Mime::Type.lookup_by_extension(parameters[:format])]
       end
 
+      # Sets the \formats by string extensions. This differs from #format= by allowing you
+      # to set multiple, ordered formats, which is useful when you want to have a fallback.
+      #
+      # In this example, the :iphone format will be used if it's available, otherwise it'll fallback
+      # to the :html format.
+      #
+      #   class ApplicationController < ActionController::Base
+      #     before_filter :adjust_format_for_iphone_with_html_fallback
+      #
+      #     private
+      #       def adjust_format_for_iphone_with_html_fallback
+      #         request.formats = [ :iphone, :html ] if request.env["HTTP_USER_AGENT"][/iPhone/]
+      #       end
+      #   end
+      def formats=(extensions)
+        parameters[:format] = extensions.first.to_s
+        @env["action_dispatch.request.formats"] = extensions.collect do |extension|
+          Mime::Type.lookup_by_extension(extension)
+        end
+      end
+
       # Receives an array of mimes and return the first user sent mime that
       # matches the order array.
       #