Question

Prior to iOS 6, we were supposed to

- (void)viewDidUnload {
   self.someDelegate = nil;
   [super viewDidUnload];
}

Now that viewDidUnload is deprecated, where do we set our delegates to nil? Thanks!

Answer 1

Views are no longer unloaded when receiving a memory warning in iOS6. So the view is never unloaded on such cases and viewDidUnload is never called in iOS6.

If you really want to mimic the old behavior (unloading the view upon receiving a memory warning) you now have to implement this behavior in the didReceiveMemoryWarning method of your view controller, after testing that the self.view.window property is nil (meaning the view is not on screen anymore, thus will be “unloaded”, meaning that you are in the same situation as the old viewDidUnload case).

-(void)didReceiveMemoryWarning
{
    if (self.isViewLoaded && !self.view.window)
    {
        // If view already loaded but not displayed on screen at this time (not attached to any window) then unload it
        self.view = nil;

        // Then do here what you used to do in viewDidUnload
        self.someDelegate = nil;
        ...
    }
    [super didReceiveMemoryWarning];
}

But note that if you use ARC and iOS5+, you generally won’t need to set your delegate to nil anymore, thanks to the weak property attribute and the Zeroing-Weak-References mechanism that automatically reset weak variables and properties to nil if the object they are pointing to does not exist anymore (thus avoiding dangling pointers).

[EDIT] And as explained by @Martin R in the comments, views are not unloaded anymore when receiving a memory warning in iOS6, so you won’t have to manage this case of receiving a memory warning and think about releasing your delegate there as this use case won’t occur anymore in iOS6.