When should an NSDocument stop being an NSWindow's delegate?

[David Chisnall]

I am currently experiencing some crashing due to an NSWindow's  
_performClose method being called after the document (which was its  
delegate) is freed.  It looks like there is something wrong in the  
NSDocument infrastructure, because the _window ivar is never retained  
by NSDocument, but it is released on -dealloc (possibly this should be  
a -performClose or similar, because NSWindow is meant to retain itself  
and release itself when it is closed?).

This usually doesn't make much difference, because the window  
controller takes ownership, and then sets the _window ivar in the  
document to nil, and so the release message is sent to nil instead of  
the window.

The problem comes if you follow the common pattern of setting the  
document (the file's owner) as the window's delegate in the nib.  In  
order for this not to crash when the window sends a  
respondsToSelector: message to the delegate while closing, the  
document must remove itself as the delegate before it exists.  This  
would be easy, except that the window controller has stolen the window  
and the window controller itself has removed itself from the array of  
window controllers by the time -dealloc is called, so there is no way  
for an NSDocument subclass to get the window in -dealloc and do this  
removal...

David

-- Sent from my Apple II