iphone - 当存在委托(delegate)时，respondsToSelector 的行为如何？

Question

我最近尝试子类化 UITextField 并将委托(delegate)设置为我自己(发现这试图解决我的问题:http://www.cocoabuilder.com/archive/cocoa/241465-iphone-why-can-a-uitextfield-be-its-own-delegate.html)

@interface MyObject :UITextField <UITextFieldDelegate>
@end

@implementation MyObject

-(id) initWithFrame:(CGRect) frame
{
  if((self=[super initWithFrame:frame]))
  {
      self.delegate=self;
  }
  return self;
}

-(BOOL) respondsToSelector:(SEL)selector
{
    NSLog(@"responds to selector");
    return [super respondsToSelector:selector];
}

// Implement all the missing methods
@end

调用接口(interface)上定义的方法会导致无限递归。我在 Apple 文档中没有看到任何内容定义在有委托(delegate)的情况下respondsToSelector 应该如何表现。

Answer 1

docs对于 respondsToSelector 声明如下:

You cannot test whether an object inherits a method from its superclass by sending respondsToSelector: to the object using the super keyword. [..] 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

看来这可能是导致您的递归问题的原因。我不知道委托(delegate)的事情是否相关。不过只是猜测。