respond_to (ActionController::MimeResponds::InstanceMethods)

    # File lib/action_controller/mime_responds.rb, line 101
          def respond_to(*types, &block)
            raise ArgumentError, "respond_to takes either types or a block, never bot" unless types.any? ^ block
            block ||= lambda { |responder| types.each { |type| responder.send(type) } }
            responder = Responder.new(block.binding)
            block.call(responder)
            responder.respond
          end