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Re: KVO: I get called on change, but then can't get the object
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Re: KVO: I get called on change, but then can't get the object


  • Subject: Re: KVO: I get called on change, but then can't get the object
  • From: j o a r <email@hidden>
  • Date: Sat, 31 May 2008 00:32:30 -0700


On May 31, 2008, at 12:21 AM, Rick Mann wrote:

I registered to observe changes in the "number" column of my tree controller:

	[mItemsController addObserver: self
		forKeyPath: @"selection.number"
		options: (NSKeyValueObservingOptionNew)
		context: NULL];

My -observe: action gets called, but this line

NSLog(@"Value changed %@: %@ (%@)", inKeyPath, inChange, [inObject selection]);

dumps this to the console:

Value changed selection.number: {
   kind = 1;
   new = <null>;
} (<_NSControllerObjectProxy: 0x177cb0>)

Note that "new" is null. I would expect it to be the value of the number.


Search for "NSKeyValueObservingOptionNew" here:

	<http://homepage.mac.com/mmalc/CocoaExamples/controllers.html>


Furthermore, this line:

	NSLog(@"selection: %@", [inObject valueForKey: @"selection"]);

dumps:

	selection: <_NSControllerObjectProxy: 0x177cb0>

But if I change it to @"selection.number", it throws the exception:

"[<NSTreeController 0x1722e0> valueForUndefinedKey:]: this class is not key value coding-compliant for the key selection.number."


What happens if you call "-valueForKeyPath:" instead of "-valueForKey:"?

j o a r


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      • From: Rick Mann <email@hidden>
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 >KVO: I get called on change, but then can't get the object (From: Rick Mann <email@hidden>)

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