form_for example for namespaced routes. Closes #9769 [sjgman9]

git-svn-id: http://svn-commit.rubyonrails.org/rails/trunk@7799 5ecf4fe2-1ee6-0310-87b1-e25e094e27de

actionpack/lib/action_view/helpers/form_helper.rb

@@ -136,6 +136,12 @@ module FormHelper
       #     ...
       #   <% end %>
       #
+      # And for namespaced routes, like admin_post_url: 
+      #
+      #   <% form_for([:admin, @post]) do |f| %>
+      #    ...
+      #   <% end %>
+      #
       # === Customized form builders
       #
       # You can also build forms using a customized FormBuilder class. Subclass FormBuilder and override or define some more helpers,