perform_action

# File actionpack/lib/action_controller/base.rb, line 1329
      def perform_action
        if action_methods.include?(action_name)
          send(action_name)
          default_render unless performed?
        elsif respond_to? :method_missing
          method_missing action_name
          default_render unless performed?
        else
          begin
            default_render
          rescue ActionView::MissingTemplate => e
            # Was the implicit template missing, or was it another template?
            if e.path == default_template_name
              raise UnknownAction, "No action responded to #{action_name}. Actions: #{action_methods.sort.to_sentence(:locale => :en)}", caller
            else
              raise e
            end
          end
        end
      end