Re: NSNotificationCenter problem

[Wolfgang Lux]

Am 01.11.2007 um 19:48 schrieb Truls Becken:

> On Nov 1, 2007 11:15 AM, Andreas Höschler <ahoesch@smartsoft.de>  
> wrote:
> > Any idea how this can be tracked done efficiently (with gdb)? Under
> > GNUstep I would raise an exception in if  removeObserver
> > notificationName is SOInvalidatedAllObjectsInStoreNotification but on
> > MacOSX I cannot simply alter and recompile the code of
> > NSNotificationCenter.
>
> There is a trick known as method swizzling that lets you replace a
> method and call the original implementation.
>
> Basically, you add a method with a new name and have it call itself.
> Then you swap (or swizzle) the implementations of the two methods, so
> that your method goes by the name of the one you want to replace. When
> your method sends a message with the new selector, it will actually
> execute the original implementation.
>
> For code and more info, see http://www.cocoadev.com/index.pl? 
> MethodSwizzling

The other option (though now deprecated in Leopard) is to write a
subclass of NSNotificationCenter which implements removeObserver and
then call +poseAsClass: at a suitable point during the initialization
of your program.

Wolfgang