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Re: Weak references & GC

From: Richard Frith-Macdonald
Subject: Re: Weak references & GC
Date: Wed, 19 Feb 2003 10:21:51 +0000

On Wednesday, February 19, 2003, at 06:19  am, James Knight wrote:

Hi, I recently have been hit with some crashing bugs in my app that uses gnustep with GC, and traced it back to the fact that NSNotificationCenter uses disguised pointers so that the GC doesn't keep the referenced objects around. However, when the object disappears, the observation is not cleared. In non-GC mode it's clearly the user's responsibility to clear the observation in the -dealloc method. However, in GC mode, I feel the system should be doing this for you. The following patch accomplishes this, and does not affect non-GC mode at all.

I kind of assumed that objects registering themselves as observers would use the gcFinalize method to remove themselves as observers when they are garbage collected... like the removal in the dealloc method where GC is not used.

While I'm sympathetic to the idea that the system might automatically remove observer when they are deallocated, this would be a difference between the GC and non-GC methods of operation (which might lead to a little confusion), and more importantly, it would be inconsistent/confusing if the notification system did this but other classes using weak references didn't.

So ... if we intend to have automatic removal of observers from notification centers when operating with GC, we should also do the same for any other occurrences of weak references ...

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