How should I remove all items from an NSTableView controlled by NSArrayController?

Question

I'm using an NSArrayController, NSMutableArray and NSTableView to show a list of my own custom objects (although this question probably applies if you're just showing a list of vanilla NSString objects too).

At various points in time, I need to clear out my array and refresh the data from my data source. However, just calling removeAllObjects on my NSMutableArray object does not trigger the KVO updates, so the list on screen remains unchanged.

NSArrayController has no removeAllObjects method available, which seems really weird. (It does have addObject, which I use to add the objects, ensuring the KVO is triggered and the UI is updated.)

The cleanest way I've managed to cause this happen correctly is:

[self willChangeValueForKey:@"myArray"];
[myArray removeAllObjects];
[self didChangeValueForKey:@"myArray"];

...so I'm kind of having to do the KVO notification manually myself (this is in my test app class, that contains the myArray property, which is NSMutableArray, as mentioned.)

This seems wrong - is there a better way? From my googling it seems a few people are confused by the lack of removeAllObjects in NSArrayController, but haven't seen any better solutions.

I have seen this solution:

[self removeObjectsAtArrangedObjectIndexes:
  [NSIndexSet indexSetWithIndexesInRange:
    NSMakeRange(0, [[self arrangedObjects] count])]];

but this looks even more unpleasant to me. At least my solution is at least marginally self-documenting.

Did Apple not notice that sometimes people might want to empty a list control being managed via an NSArrayController object? This seems kind of obvious, so I think I must be missing something...

Aside: of course, if I add new items to the array (via NSArrayController), then this triggers a KVO update with the NSArrayController/NSTableView, but:

1. Sometimes I don't put any items in the list, because there are none. So you just see the old items.
2. This is a bit yucky anyway.

Answer 1

You don't remove items from a table view. It doesn't have any items—it just displays another object's items.

If you bound the array controller's content array binding to an array property of some other object, then you should be working with that property of that object. Use [[object mutableArrayValueForKey:@"property"] removeAllObjects].

If, on the other hand, you haven't bound the array controller's content array binding, then you need to interact with its content directly. Use [[arrayController mutableArrayValueForKey:@"content"] removeAllObjects]. (You could also work with arrangedObjects instead of content. If one doesn't work, try the other—I've only ever done things the first way, binding the array controller to something else.)

Answer 2

Had this problem as well and solved it this way:

NSArrayController* persons = /* your array controller */;
[[persons content] removeAllObjects];