objective-c - 什么是 class_setIvarLayout 和 class_getIvarLayout？

Question

我正在尝试在运行时动态创建 objc 类，我需要Ivar在创建的类中添加一些。我发现class_addIvarwhich 应该做我想做的事，但我也发现了这些功能：

• class_setIvarLayout
• class_getIvarLayout
• class_getWeakIvarLayout
• class_setWeakIvarLayout

该文档并没有真正说明有关这些方法的任何有用信息，我也无法从网上找到任何有用的解释。那么它们是什么？如果我想做一些事情，我需要使用它们Ivar吗？

Answer 1

The class_*IvarLayout methods are used by the garbage collector (if/when you're using it) to determine which areas of an object's memory need to be scanned for strong/weak references.

It's unlikely you'll ever need to call these methods; the appropriate layouts are generated when you call objc_registerClassPair.