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分类与扩展的区别？ #27

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tbfungeek opened this issue Jan 5, 2020 · 0 comments

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tbfungeek commented Jan 5, 2020 •

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分类是运行时决议的，扩展是编译时决议的
分类不可以添加实例变量，扩展可以添加实例变量
分类可以在没有源码的情况下为某个类添加方法，扩展只能寄生于宿主类的.m文件中，在编译期和头文件里的@interface以及实现文件里的@implement一起形成一个完整的类。伴随着类的产生而产生，也随着类的消失而消失。没有源码的情况下不能为某个类添加方法。

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