# 08.load与-initialize

## + load

* 当类对象被引入时,runtime会向每一个类对象
* load方法会在每一个类甚至分类被引入时仅调用一次.
* 调用的顺序是:
  * 父类优先于子类,子类优先于分类
* load方法不会被自动继承
  * 子类中没有+load方法时系统不会多次调用父类+load

### 使用场景

* Method Swizzle

## + initialize

* 第一次使用这个类的时候会调用这个方法-懒加载
  * 会在第一次使用第一个类方法或实例方法之前被调用

### 使用场景

* 初始化全局变量或静态变量
* load方法会被子类/分类继承
  * 如果子类没有实现+initialize方法,会调用父类的+initialize方法


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