KVO and NSMutableArray

objective-c cocoa key-value-observing
Zingu picture Zingu · Aug 2, 2011 · Viewed 9.1k times · Source

How can I set KVO (key-value-observing) with an NSMutableArray?

I want to be notified when a change appears in the array. I never used KVO before with a collection like an array.

Answer

Joe Osborn picture Joe Osborn · Aug 2, 2011

I think you'll be interested in the answers to this question.

The key is that you can't observe any properties on the array directly—the array is just storage—but you can observe the to-many relationship that's backed by that array (here I'm assuming your array is a property on an object somewhere).

If you don't want to use those special accessors all over the place, your code that owns the array can call

-willChange:valuesAtIndexes:forKey: and

-didChange:valuesAtIndexes:forKey:

as described in this answer.

And if you're on a Mac and not iOS, you should consider NSArrayController.

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