On Aug 8, 2012, at 4:21 PM, Graham Cox <graham....@bigpond.com> wrote: > On 09/08/2012, at 9:10 AM, Graham Cox <graham....@bigpond.com> wrote: >> Ah, I'm thinking this *could* be due to my previous observation about cells >> being copied using NSCopyObject. If the cells are copied during that >> animation for some reason, then perhaps the text settings for my custom cell >> are not being copied, since I'm alloc/initing a new cell in copyWithZone: >> instead of relying on super's implementation. I'll follow along with that >> line of thought.... > > Yep, that seems to be the issue. > > This opens up a whole big can of worms about implementing copy. > > If a superclass implements copies using NSCopyObject, then any pointer ivars > we add in a subclass need to be additionally -retained. But if the superclass > implements copy by alloc/initing a new object and setting properties, then > this extra step would lead to an over-retain and so leak. > > But how can we know what approach the superclass has taken? It's not > documented and we don't have the source. Aren't we supposed to be immune from > implementation details like this? Or is it just a case of after a while the > experienced Cocoaista "just knows" what to do in each case? This is only just > rearing its head for me after almost 10 years...
NSCopyObject() is ugly. Avoid it if you can. NSCell uses NSCopyObject. I don't know if there are other framework classes that are likely to be copied and subclassed that use NSCopyObject. One solution is to compile your subclass with ARC. ARC-compiled ivars get correct retain count management inside NSCopyObject. (You still need to override -copyWithZone: if you want those ivars to be copied instead of retained, though.) -- Greg Parker gpar...@apple.com Runtime Wrangler _______________________________________________ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) 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 arch...@mail-archive.com
