super class 调用的 respondsToSelector

Question

我有以下方法：

- (void) someMethod
{
    if ([super respondsToSelector:@selector(someMethod)])
    {
        [super performSelector:@selector(someMethod)
                    withObject:nil];
    }
}

someMethod 不存在于 superclass 上。据我所知，如果没有这样的方法，运行时将向链中的下一个响应者询问这样的方法，直到 NSObject class。而且我确信，if 语句将 return 否。

声明return是的。之后它执行选择器而不会崩溃。结果 - 无限递归。

所以，我有两个问题：

为什么 [super respondsToSelector:@selector(someMethod)] return 是？
为什么 [super performSelector:@selector(someMethod) withObject:nil] 不会因错误 'does not responds to selector' 而崩溃？

我想我错过了一些重要的东西。请帮忙。

Answer 1

是的，您错过了您建议的重要内容。来自 respondsToSelector:

的文档

You cannot test whether an object inherits a method from its superclass by sending respondsToSelector: to the object using the super keyword. This method will still be testing the object as a whole, not just the superclass’s implementation. Therefore, sending respondsToSelector: to super is equivalent to sending it to self. Instead, you must invoke the NSObject class method instancesRespondToSelector: directly on the object’s superclass, as illustrated in the following code fragment.

if( [MySuperclass instancesRespondToSelector:@selector(aMethod)] )
{
   // invoke the inherited method
   [super aMethod];
}

HTH

super class 调用的 respondsToSelector

respondsToSelector for super class invocation

ios

objective-c

polymorphism

objective-c-runtime