Re: [RESOLVED] Re: Curious about copyWithZone message from NSArrayController in "GC required" project

FROM : Luke Evans
DATE : Fri Feb 15 01:43:03 2008

Closure:

Not that this is necessarily of any use to anyone, but the "something 
seriously wrong" causing -copyWithZone to be sent to an 
NSManagedObject was the following:

I had an NSArrayController set up to collect a set of NSManagedObjects 
from a master view selection 'upstream'.  I had then bound a table 
view to this in one of its columns, *but* I had only set the 
Controller Key (to arrangedObjects), I had not entered a Model Key 
Path i.e. set up a path to the content to be rendered in each cell of 
the column.

Under these circumstances, the objects referenced in arrangedObjects 
(which happen to be Core Data objects) get sent a -copyWithZone.

So this is why the problem "went away" when I had restructured my 
bindings before, I had clearly 'done the right thing' and the problem 
vanished.  I've just repeated the earlier mistake and so can report 
the reason for the message.

-- Lwe

On 13-Jan-08, at 3:37 PM, Luke Evans wrote:

> O.K...
>
> So, I just did this and found it wasn't being called any longer. 
> So, I suspect your original intuition was right - there was 
> something badly wrong with my code (which thankfully I have now 
> rectified - though its frustrating not to be able to nail the 
> original reason now).
>
> One change that may have had a bearing here was that I had 
> inadvertently commented out some code to return an 
> NSCollectionViewItem in a subclass of NSCollectionView that was 
> generating UI for the B objects.  I fixed this yesterday.  It's 
> possible that something in NSCollectionView was trying to do its 
> best with just the prototype item and the list of B's from the 
> NSArrayController.  Anyway, that's pure speculation, and perfectly 
> well covered by your comment that "something is seriously wrong with 
> your code"!
>
> I'm deleting the spurious copyWithZone now, safe in the knowledge 
> that it's just not something that I should need to implement until 
> such time as I have a real need for a copy constructor in that class.
>
> Thanks.
>
> -- Lwe
>
>
> On 13-Jan-08, at 2:54 PM, Bill Bumgarner wrote:
>

>> You mentioned that you had implemented a -copyWithZone: on B?  Can 
>> you set a breakpoint on that and see what backtrace barfs up as a 
>> result?

>
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