Re: Weak references & GC

[Richard Frith-Macdonald]

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 ...