Hi List,in the course of debugging a -dealloc in a data structure that is part of an NSDocument app, I've discovered that my document and all it's data never gets deallocated. After some extensive digging I nailed the problem down to mutual retain cycles (not sure this is the right term). I actually had a number of those, it always followed this scheme:
An object A was retained by an object B which was owned by A. A releases B in its -dealloc, B releases A in its -dealloc. Since neither retain count would ever go to zero, neither dealloc would ever be called and everything would just stay there forever.
By changing the reference from B to A to a weak reference which doesn't retain and release A, the problem goes away. However, generally speaking this is dangerous road to go (and against memory management guidelines) because now it's no longer guaranteed that A still exists if B is using it. Sure, there could be measures implemented that help with that (like A notifying B that it's going away) but that would mean a lot of additional housekeeping.
Defining who owns who (owners get a strong reference to owned) also helps, because it's then guaranteed that A will be there for as long as B exists, thus a strong reference is not needed. But there are still cases where it is unknown which of the objects is going to be released first (because it's hidden in the inner workings of AppKit for example).
I'm wondering if there is a general rule or mechanism that suggests what to do in such a case. For instance, how are delegates implemented in AppKit, are they retained? If so, when are they released. It can't be in -dealloc, otherwise everything would lock itself out of deallocation?
Thoughts? Markus -- __________________________________________ Markus Spoettl
smime.p7s
Description: S/MIME cryptographic signature
_______________________________________________ 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: http://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to [EMAIL PROTECTED]
