Why don't you use viewWillAppear and viewDidDisappear, to register and 
unregister observers to your foo property object?

If you don't use ARC, be carefull to unregister on dealloc too!

> El 05/06/2014, a las 09:30, Rick Mann <[email protected]> escribió:
> 
> 
>> On Jun 5, 2014, at 00:26 , Lee Ann Rucker <[email protected]> wrote:
>> 
>> If you're doing something like this:
>> 
>> - (void)setFoo: (Foo *)aFoo
>> {
>> [foo removeObserver:self forKeyPath:@"whatever"...];
>> foo = aFoo;
>> [foo addObserver:self forKeyPath:@"whatever"...;
>> }
>> 
>> we used that pattern for a while but were constantly getting bit by 
>> observers on objects being dealloced or KVO firing and triggering unwanted 
>> side effects if we called setFoo: in dealloc. So we did a complete switch 
>> over to doing
>> 
>> [self addObserver:self forKeyPath:@"foo.whatever"...
>> 
>> in init, and removeObserver in dealloc, because you can remove an observer 
>> on yourself in dealloc without the "observers still registered" warning.
>> 
>> Since it's on self, you can set it before foo exists, and setFoo: triggers 
>> it. Plus we could use synthesized setters.
> 
> I collect the removeObserver calls into an "ignoreFoo" method, and similarly 
> the addObserver in an "observeFoo" method. Then in -dealloc I call 
> -ignoreFoo. I've never run into the (annoying) registration mismatch errors.
> 
> Your suggestion is a good one, but I don't think it solves the problem I have 
> of -setFoo: being called before -viewDidLoad (before the IBOutlets are 
> non-nil).
> 
> -- 
> Rick
> 
> 
> 
> 
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