一句话Design Pattern：Command

定义：The Command Pattern encapsulates a request as an object, thereby letting you parameterize other objects with different requests, queue or log requests, and support undoable operations.

一句话：把一个request写成一个object扔给另一个component来执行。

类比：和在点菜单上勾选吃食然后命令厨房去做是一个道理。