objective-c - class_getClassVariable() 有什么作用？

Question

如果实例变量属于一个类的一个实例，我认为类变量将属于一个元类的实例。但我使用 Objective-C 元类的经验告诉我，这不太可能。

我想知道 class_getClassVariable 相对于 class_getInstanceVariable 做了什么，以及为什么在运行时没有 class_setClassVariable。

Answer 1

我在这里找到了关于它的讨论: http://lists.apple.com/archives/objc-language/2008/Feb/msg00021.html

Nope, it's not possible. There is no compiler support, and there is no runtime support; class_getClassVariable(cls, name) merely calls class_getInstanceVariable(cls->isa, name).

If it were possible, it likely would not give you a new variable on each subclass anyway. Objective-C's metaclasses are not quite first- class enough for that to work well.