KVO bug?

FROM : Matteo Manferdini
DATE : Sat Jun 03 20:18:36 2006

Hi everyone. I'm trying to get arrays for removed and added items in 
a KVO observed array. But, when I look into the change dictionary 
(using NSKeyValueChangeOldKey and NSKeyValueChangeNewKeys) i get a 
NSNull object instead of the arrays.
I noticed in mmalc'c GraphicsBinding sample (on http://
homepage.mac.com/mmalc/CocoaExamples/controllers.html) the following 
comment:

/*
Should be able to use
NSArray *oldGraphics = [change objectForKey:NSKeyValueChangeOldKey];
  etc. but the dictionary doesn't contain old and new arrays...??
*/

So is this a bug in Cocoa KVO? Do I have to do it manually or there 
is a way to make it work?
Thank you very much.

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Matteo Manferdini