Question

I have an NSCollectionView whose content is bound to an NSArrayController’s arrangedObjects. When I call addObject: on the array controller, it seems to reallocate the underlying array – I can observe the pointer changing addresses. This isn’t acceptable behavior for my particular case, as other objects also depend on the array.

Is this normal behavior or am I doing something wrong? I’ve seen some alternative solutions, such as directly modifying the array and calling willChangeValueforKey: and didChangeValueForKey: on the controller, but that doesn’t seem like the most elegant solution.

I am fairly new to Objective-C and Cocoa, so go easy on me. 🙂

Thanks!

Answer 1

@interface NSArrayController : NSObjectController {
@private
    void *_reserved4;
    id _rearrangementExtensions;
    NSMutableArray *_temporaryWorkObjects;
    NSUInteger _observedIndexHint;
    NSMutableIndexSet *_selectionIndexes;
    NSMutableArray *_objects;
    NSIndexSet *_cachedSelectedIndexes;
    NSArray *_cachedSelectedObjects;
    NSArray *_arrangedObjects;
}

If you look at NSArrayController’s header, the instance variable for arrangedObject is a NSArray, so it will have to create a new array whenever you add a new object and is a normal behaviour.