The command design pattern

The command design pattern which provides undo-redo operation, is applied to the whole class frame design and several sub-classes design of graphics edit operation.

命令模式的使用包含整个类框架设计和几套图形编辑操作子类设计，支持可以撤销重做的操作。

The Command design pattern provides a way to encapsulate behavior in a class with well-known execution semantics. Listing 4 shows the result of applying these two patterns to the code in Listing 3.

公共设计模式提供了利用常规执行语句来在类中封装行为的方法。

I am learning command design pattern. As far as I know, four terms always associated with the command pattern are command, receiver, invoker and client.

我在学习命令设计模式。据我所知，总是与命令模式相关的四项命令，接收，调用和客户端。