I have searched design patterns where my subject and observer can be changed at any time, but I failed.

我搜索的设计模式在我的题目和观察员可以在任何时间改变，但我失败了。

youdao

I have searched design patterns where my subject and observer can be changed at any time, but I failed.

我搜索的设计模式在我的题目和观察员可以在任何时间改变，但我失败了。

youdao