Re: Key Value Observation is over reacting

[Markus Hitter]

Am 13.12.2007 um 21:12 schrieb Fred Kiefer:

>  I just see that this special case is not
> failing there. Should I set breakpoints on methods of the watched
> instance and check the back trace for on the fly methods?

Yes, why not?

As for the remaining part, I can't see when the getter method would  
be used inside KVO at all. Notifications are sent on value changes  
only, which does the setter. Where does the conflict arise?

Until today, I always thought KVO is based on a mini notification  
center inside NSObject's -setValue:forKey:. This method would try a  
few ways to get the variable set, then send a notification to all  
subscribers on success. No need to patch existing classes.

However, this morning I learned, Apple uses something they call "isa- 
swizzling":

<http://developer.apple.com/documentation/Cocoa/Conceptual/ 
KeyValueObserving/Concepts/KVOImplementation.html#//apple_ref/doc/uid/ 
20002307>


Markus

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Dipl. Ing. Markus Hitter
http://www.jump-ing.de/