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Editorial Team
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Asked: 2026-05-22T03:26:17+00:00

I would like to observe a property on models contained in an NSArray. I

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I would like to observe a property on models contained in an NSArray. I can’t use a keyPath of “arrayOfModels.property”, because NSArray throws an exception on 

- (void)addObserver:(NSObject *)observer forKeyPath:(NSString *)keyPath options:(NSKeyValueObservingOptions)options context:(void *)context;

Instead, the docs say to use

- (void)addObserver:(NSObject *)observer toObjectsAtIndexes:(NSIndexSet *)indexes forKeyPath:(NSString *)keyPath options:(NSKeyValueObservingOptions)options context:(void *)context;

So does that mean I’d also have to listen to “arrayOfModels” itself, so that when its elements change, I can remove listeners from the old elements and attach them to the new elements? I was hoping KVO would be awesome enough to take care of this for me somehow…

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1 Answer

  1. Editorial Team

    Doesn’t seem like there’s a built-in way to do this, so I’m just removing old listeners and adding new ones when the array membership changes.

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