KVO and NSMutableArray

问题:

how can I set KVO 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.

回答1:

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.

回答2:

You can use KVOMutableArray. It is a subclass of NSMutableArray, and it supports KVO.

disclaimer: I am the author :)