发送isEqual：到nil总是返回NO

本文介绍了发送isEqual：到nil总是返回NO的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！ 问题描述

如果你发送isEqual：给一个恰好是nil的对象，你总是得到NO。

If you send isEqual: to an object that happens to be nil, you always get NO back.

这是预期的行为吗？要成为一个功能而不是一个错误，我会期望它返回是如果其他对象也是nil，否则否则？语义上这似乎是正确的行为。

Is this the expected behavior? To be a feature instead of a bug, I would expect it to return YES if the other object is also nil, and NO otherwise? Semantically this seems the correct behavior.

如果我的期望不正确，推荐的过程？发送isEqual：（和朋友）之前检查nil？

In case my expectations are incorrect, what the recommended proceedure? Check for nil before sending isEqual: (and friends)?

推荐答案

是的，这是预期的行为。对nil的任何消息将返回一个结果，对于请求的类型，结果等于0。因为布尔值的0是NO，那就是结果。

Yes, this is the expected behavior. Any message to nil will return a result which is the equivalent to 0 for the type requested. Since the 0 for a boolean is NO, that is the result.