In object-oriented programming, a metaclass is a class whose instances are classes.
Just as an ordinary class defines the behavior of certain objects, a metaclass defines the behavior of certain classes and their instances.
也就是說metaclass的實例化結果是類,而class實例化的結果是instance。
應用場景就是動態的修改類
https://www.liaoxuefeng.com/wiki/897692888725344/923030550637312
我也看不懂