Is there a way to trap messages sent to nil in Objective-C?

Question

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?

Answer 1

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

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