有没有办法在Objective-C中将消息发送到零？ [英] Is there a way to trap messages sent to nil in Objective-C?

问题描述

我刚刚被一个令人讨厌的错误所困扰， Objective-C中的发送消息到nil是行。

我看过发送消息到nil？，并且共识似乎是在Objective-C中我们如何滚动。

现在，也许我在Objective-C上没有足够的经验，但是看起来这样做是有用的，因为我不能想到这个应该发生的好原因大部分的时间。然而，它可能只是一个编码成语，我还没有习惯。

所以除了这样检查无处不在：

  assert（object！= nil）; 
 [object message]; 
  

有没有办法使运行时陷阱这个条件，并在对象是否为nil？

解决方案

您可以使用（请参阅dtrace解决方案的注释）.bake / 2008/01/02 / objective-c-logging-messages-to-nil /rel =noreferrer 。

  pid $ 1 :: objc_msgSend：entry 
 / arg0 == 0 / 
 {
 ustack（）; 
} 
  

I've just been bitten by an annoying bug that was made obscure by the "send message to nil is ok" behaviour in Objective-C.

I've seen Sending a message to nil?, and the consensus seems to be 'thats how we roll' in Objective-C.

Now, maybe I don't have enough experience in Objective-C, but it seems like it would be useful to trap this, because I can't think of a good reason why this should be happening most of the time. However, It could just be a coding idiom I'm not used to yet.

So other than checking for nil everywhere like so:

assert( object != nil );
[object message];

Is there a way to make the runtime trap this condition, and warn when object is nil?

解决方案

You could use a ObjC undocumented trick or dtrace (see the comments for the dtrace solution).

pid$1::objc_msgSend:entry
/arg0==0/
{
  ustack();
}

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