I have a specific NSToolbarItem subclass. There need to be multiple instances in a toolbar. I overrode -allowsDuplicatesInToolbar though that never gets called. So, to ensure that I get separate instances, I implemented -toolbar:itemForItemIdentifier:willBeInsertedIntoToolbar: to create a new instance every time.
The odd thing is that it only gets called for this specific subclass. I can't figure out why it doesn't get called for the other toolbar items. They are all created and loaded from a xib. Now, in this particular case, I only care about this one particular subclass so it works for my current purposes but this seems a bit fragile and I'd like to know the logic here.