NSURLConnection still calls delegate AFTER cancel method has been called

Question

Hi All, Having a problem with NSURLConnection, if I create a NSURLConnection and call [connection connectionWithRequest] let it load a little then call [connection cancel] most of the time that works fine. However occasionally even after I call [connection cancel] the connection's delegate still gets called (which crashes the app). Googling around it looks like the problem here is a race condition in the runloop, I cancel the connection and release the delegate but before the runloop cycles it calls the delegate functions -> crash.

Is there a way for me to, after I call [connection cancel] confirm the connection has actually canceled? Even a crappy while() loop will do :(

Answer 1

You should not release the connection & associated storage until it your delegate receives either a connectionDidFinishLoading: or a connectionDidFailWithError: message.

Delegates are normally retained by the object they're acting as delegate for, so the delegate shouldn't become invalid while the NSURLConnection is still referring to it, unless you're over-releasing it somehow.

Answer 2

You could use [connection setDelegate:nil] perhaps.

However, assuming you haven't created extra threads, there should be no way to get a race condition as the cancel call and event delivery will be on the same thread. As David hints at, I'd examine your code, check for any odd cases like connection getting set to nil before the cancel call, or problems with object retain/release calls.

This link might be useful if there's a possibility objects are being overreleased:

http://www.frogameleon.com/blog/last-night-an-iphone-zombie-nszombieenabled-saved-my-life