Re: NSDocument never deallocated with autosave/versions
Re: NSDocument never deallocated with autosave/versions
- Subject: Re: NSDocument never deallocated with autosave/versions
- From: Graham Cox <email@hidden>
- Date: Wed, 30 May 2012 13:30:25 +1000
Well well.
This leak only occurs if I have sandboxing enabled. What a surprise!
The save dialog is not releasing the document when it closes if sandboxing is turned on. If I repeatedly close the window but cancel the save dialog, the retain count goes up by about 9 counts each time.
Sandboxing is simply not ready for prime time, and I feel very frustrated that it is now compulsory for the App Store when it is this broken.
--Graham
On 30/05/2012, at 12:05 PM, Graham Cox wrote:
> I've got a large memory leak in my app because my document class is never deallocated once I've added content to it.
>
> I've been over it with a fine-toothed comb and I'm prepared to say it doesn't look as if I'm doing anything wrong. I overrode -retain and set a breakpoint there, so I could see who is retaining the document. Of course, many, many objects do in the complicated new world of autosaving, versions and blocks.
>
> Every single retain on NSDocument comes from the internals of Cocoa - my code never retains the document at all.
>
> The key object that seems never to release my document is the NSSavePanel that is displayed only when I have added content, and I close the window. The save panel is shown, and the retain count shoots right up. If I click 'Don't Save', the window closes as expected but the document is still retained - the retain count does not go back down to the point it was at prior to the dialog showing up, and dealloc is never called.
>
> Key point: If I disable autosaving for my document class, the document is deallocated as expected.
>
> What I want to know is, is this behaviour correct? It doesn't seem to be correct but it could be - perhaps Versions is retaining my document after its normal lifetime for its own purposes? Obviously I understand that peeking retain counts is a bad strategy for debugging, but just looking at the general trend here, the document ticks over at about a retain count of 3 or 4. When the save dialog is presented, it can shoot up to 17-20 counts, and on closure this drops back to about 12. With autosave/versions disabled, it goes to zero.
>
> If Versions is retaining documents for some reason, fair enough, I guess I have to accept it. But it causes awkward bugs because of the clean up I expect to do in -dealloc, like unsubscribing from notifications and so on. I'm also a bit uneasy about having large objects like this which are heavily customised in my app hanging around because Cocoa thinks it knows what to do with them - surely it can't know how a particular class has been subclassed and always do the right thing? The way Versions works seems really quite scary to me.
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