On Apr 27, 2010, at 11:58 AM, vincent habchi wrote:
Yet, at the same time, you may want the dealloc: method to trigger some events. For example, if you have a CALayer that holds various sublayers, and that CALayer goes away, you may want all the sublayers to go away at the same time. Yet, this is impossible if some other object around locks a reference to the sublayers.
Most of the time you just want your -dealloc method to call -release on objects it holds references to. Or you might need to clean up some external resource (like closing a file), although it's often better to have an explicit -close method on your class to do this.
In your example, it doesn't matter if the sub-layers stay around, because they won't have a parent layer so won't be visible or consume any graphics resources. If you somehow forced those sub-layers to get dealloced at the same time as the parent layer, then any other object that had a reference to one would crash the next time it accessed it; bad news.
Remember that in a ref-counted (or GC'd) system you can't force an object to deallocate (even 'self'.) The deallocation is under control of all the other objects that have references, and the runtime itself. So you should never put any code into -dealloc or -finalize that absolutely has to run at a particular time.
By the way, how are exactly multiple calls to [object autorelease] handled by the pool? Does this give rise to as many calls to release: as they are autorelease references stored, or does the pool directly adjust the retain count?
Each call to -autorelease will cause one future -release call. So yes, the pool keeps a count of how many times -autorelease has been called for each object, and calls -release on it that many times when it drains.
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