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Re: change in model not reflected in interface




On Jul 30, 2005, at 11:17 AM, Edward Hillenbrand wrote:

- (void)didChangeValueForKey:(NSString *)key {
if ( [key isEqualToString:@"foo"] ) {
[self setBar:[self foo] * 2]; // this change is not reflected in the interface???
NSLog(@"%f", [self bar]);
}
}
@end


AFAIK, the object above is KVO complaint. I have an interface with two text fields, one bound to foo and the other bound to bar. When I change the value in the text field bound to foo the value in the text field bound to bar doesn't change.


The accessor methods are KVO compliant, but you disrupt the mechanism by overriding didChangeValueForKey: (specifically, you don't invoke the superclass's implementation -- although you shouldn't be doing this anyway: is there anywhere in the documentation that suggests that overriding the KVO notification methods is a common pattern?). It's not clear why you would do this rather than simply:


- (void)setFoo:(float)value {
    foo = value;
    [self setBar:value * 2];
}


mmalc

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References: 
 >change in model not reflected in interface (From: Edward Hillenbrand <email@hidden>)
 >Re: change in model not reflected in interface (From: Scott Quiring <email@hidden>)
 >Re: change in model not reflected in interface (From: mmalcolm crawford <email@hidden>)
 >Re: change in model not reflected in interface (From: Edward Hillenbrand <email@hidden>)



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