OC中的load和initialize方法

内容

• load
• initialize
• 参考链接

load方法

官方文档说明：

A class’s +load method is called after all of its superclasses’ +load methods.

A category +load method is called after the class’s own +load method.

在main函数之前系统会递归调用，另外需要注意的是：

1. 方法线程安全
2. 在 runtime调用 +load 方法前后是加了 objc_autoreleasePoolPush()和 objc_autoreleasePoolPop()的
3. 按照继承顺序递归调用
4. 先本类，后分类

使用场景
Method Swizzle

+ (void)load {
Method originalFunc = class_getInstanceMethod([self class], @selector(originalFunc));
Method swizzledFunc = class_getInstanceMethod([self class], @selector(swizzledFunc));

method_exchangeImplementations(originalFunc, swizzledFunc);
}

initialize

官方文档说明：

Initializes the class before it receives its first message.

The runtime sends initialize to each class in a program just before the class, or any class that inherits from it, is sent its first message from within the program.

// In Parent.m
+ (void)initialize {
  if (self == [Parent class]) {
  NSLog(@"Initialize Parent, caller Class %@", [self class]);
  }
}

使用场景
initialize方法一般用于初始化全局变量或静态变量。

参考链接

• summy的博客