Re: With What does Apple Swizzle the IsA-pointer in KVO?
Re: With What does Apple Swizzle the IsA-pointer in KVO?
- Subject: Re: With What does Apple Swizzle the IsA-pointer in KVO?
- From: Paul Sargent <email@hidden>
- Date: Fri, 23 Nov 2007 16:50:47 +0000
KVO is not based on the internals of an object (which is assumed to
be hidden), and it does not access hiddden internals. KVO is based
on KVC and uses accessors.
To expand a bit, my mental model of it is (and this could be wrong):
No Observing:
ObjA ----setBlah:----> ObjB
Observing:
ObjA ----setBlah:----> ProxyForB -----setBlah:----> ObjB
|
|
\-------blahChanged:---> Observer
i.e. When the observer registers a proxy is inserted in the chain. The
message is intercepted by the proxy and it notifies the Observer.
I don't think it's quite like this, but this allows me to understand
it enough to use it.
It's also possible for the observed object (ObjB) to send a message to
the observer with didChangeValueForKey:
I don't quite see what wanting that you don't have. Is it that you
want to know when any key has change, rather that one specific one?
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