这是一个可以多步回退的例子，使用Command模式，即可以对对象属性回退，也可以对创建和删除对象进行回退．-it to be a multi-step regression example, the use of Command mode, which can object attribute regression, but also be able to create and delete objects regression.

实现撤销和恢复功能得远吗-achieve withdrawal and recovery far?

实现撤销和恢复功能得远吗-achieve withdrawal and recovery far?

这是一个可以多步回退的例子，使用Command模式，即可以对对象属性回退，也可以对创建和删除对象进行回退．-it to be a multi-step regression example, the use of Command mode, which can object attribute regression, but also be able to create and delete objects regression.