On Nov 18, 2008, at 2:12 AM, Jonathan Hess wrote:
Which parts do you feel are contrary? I'm guessing it's that outlets with no setters are retained.
Yes, that's the root of the whole issue. The fact is that outlets without setters that are retained aren't released by the code that retained them. The responsibility for releasing them is implicitly passed on to some other code. I misunderstood this after reading that paragraph a number of times because it is simply contrary to my understanding of Cocoa memory management. I think it is contrary to the Cocoa memory management rules that the code that retains these objects isn't releasing them.
Now that I know that, there are still problems. The outlets can be released in more than one place. As mmalc mentioned, the view controller's view may be unloaded in response to a memory warning. However, the view won't be unloaded if the view controller is the frontmost view controller. There's no simple way for a view controller subclass to know if it's the frontmost view controller or therefore if its view will be unloaded. There is no viewDidUnload callback that would be the right place to release the outlets in this case. The code that mmalc showed is not correct because it doesn't take into account the fact that the frontmost view controller won't unload its view.
In effect it is the UIViewController base class that is retaining the outlets, or causing them to be retained, when the nib is loaded. But it abdicates responsibility for them. The UIViewController base class is also the class that is releasing its view without any notification to the derived class that it should also release the outlets.
I haven't decided how I'm going to fix all this. Either I'll add assign properties so the outlets are not retained or I'll release them all in viewDidLoad.
Most nib-loading on iPhone OS is done by UIViewController and I suppose most of my complaints above are with the UIViewController implementation. In my code I would hardly ever have a reason to want to retain an outlet. Having outlets be retained by default gives my code no benefit, and causes some complications.
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