def invoke(controller_class, metadata = nil)
      controller = controller_class.new call, metadata
      controller.run
    end
def invoke(controller_class, metadata = nil)
      controller = controller_class.new call, metadata
      controller.run
    end
Invoke another controller class within this controller, returning to this context on completion.

 @param [Class] controller_class The class of controller to execute
 @param [Hash] metadata generic key-value storage applicable to the controller
 @return The return value of the controller's run method