Question

I have a object that serves as a connection layer between my view controller and my webservice. This object takes a delegate and informs that delegate whenever data is returned from the server. I am running into a problem where the delegate gets dealloc’d while an http request is running. When the request returns, my object attempts to call a method on the delegate and the app crashes.

What is the best way to handle this. I have read in several places that you should not retain your delegates because very frequently they are retaining the object too, resulting in a cyclic dependence. So if I can’t retain my delegate, how do I check if it has been dealloc’d before I call methods on it?

@property (nonatomic, assign) NSObject<ServerConnectionDelegate>* delegate;

Answer 1

Usually you should use delegate pattern if life-time of the delegate is longer than lifetime of worker object. (sorry not sure about correct term here).

You have several options how to fix that:

• As a workaround you can set connection delegate to nil in your object’s dealloc method.
• If data is required (may be for some later usage) you can use NSNotification to inform delegate for any connection events instead of delegate pattern.
• As Jack suggested in his comment you can make your delegate a weak property of connection – that will probably be the best solution if your project is using ARC