After binding the title of a button in a nib, I started getting the following burps today, whenever its window was closed.
An instance 0x100c598c0 of class MyWindowController was deallocated while key value observers were still registered ... [You know the drill] ... Key path: document.foo.bar ... Thanks to some of the nice -description implementations given by Apple to their proxy things, I found the cause which was that, while this button’s title was bound to a different key path, ‘buttonTitle’ of MyViewController, MyViewController has an implementation of +keyPathsForValuesAffectingButtonTitle which returns windowController.document.foo.bar. The window controller is being deallocced before the view controller. So, although the “base” part of the binding was still intact, this keyPathForValuesAffecting was still in use when it was broken. The view controller is instantiated in the nib. The File’s Owner is the window controller, which is wired in the nib to a ‘windowController’ *outlet* of the view controller. I do this because this window contains three tabs, some of which can take a long time to load, and to improve performance I put each tab in a separate nib and load it only when the user wants to see it. Each nib contains its own view controller. In order to access the data model and document, the view controller uses key path ‘windowController.document', via this outlet. It was an architecture that I arrived at after "trying everything else", and I’ve been happy with it. Well, each of my view controller’s, and my window controller, has a -tearDown method in which I remove all the bindings and observers that would other cause this kind of burp. So I solved the problem by deleting the binding of the button’s title from the xib, and instead implementing the *exact* same binding “manually” in the view controller’s -awakeFromNib, using -bind:toObject:withKeyPath:options:, so that I could -unbind: it in my view controller’s -tearDown method. I’m wondering what went wrong here. Possible explanations: (A) My architecture is all wrong. (B) You should never put an outlet in a key path. Why not, and what alternative is there? (C) This is a very rare corner case. Forget it and move on. (D) Cocoa Bindings should be smart enough to stop observing keyPathsForValueAffecting after being notified that a window is closing. This is a bug which I should report to Apple. _______________________________________________ Cocoa-dev mailing list ([email protected]) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: https://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to [email protected]
