Re: Help debugging "Dangling reference to an invalid object." Core Data error
Re: Help debugging "Dangling reference to an invalid object." Core Data error
- Subject: Re: Help debugging "Dangling reference to an invalid object." Core Data error
- From: Ben Trumbull <email@hidden>
- Date: Mon, 2 Nov 2009 13:38:19 -0800
> On 10/29/09 5:23 PM, Ben Trumbull said:
>
>>> Even if I do [scene addTargetsWeak:[scene targetsWeak]] I get the error.
>>>
>>> Does this make any sense to anyone?
>>
>> The only caveat is you cannot change relationships from within -
>> awakeFromFetch. This is documented:
>
> Ben,
>
> This is something I know and avoid, but it turns out this is what's
> happening afterall! Thanks!
>
> Is there some way to catch such violations? I suppose I could implement
> all relationship mutating methods, call backtrace(), and look for
> awakeFromFetch. :)
Not really. But you can file a bug, and we can add an assertion to the debug library easily enough. Or we can enable change tracking in -awakeFromFetch. But that would mean generic setters will dirty newly fetched objects, and their containing documents, which people objected to, and resulted in the current behavior.
> Basically, I have a controller class that uses KVO to observe all kinds
> of things. And I'm suffering from a kind of spaghetti chain of KVO and
> faulting. In my observeValueForKeyPath:ofObject:change:context: I
> sometimes end up firing a fault of some object, which causes me to
> reenter my observeValueForKeyPath: for some other 'context', which ends
> up firing a fault of some other object, etc. At some point
> awakeFromFetch is in the backtrace and at some later point I mutate a
> relationship. Ick.
Well, you can use prefetching to disentangle dependent controllers from firing too much stuff too lazily, or custom controller classes that override
- (BOOL)fetchWithRequest:(NSFetchRequest *)fetchRequest merge:(BOOL)merge error:(NSError **)error;
- Ben
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