NSOutlineVIew Drag, drop in different window (same app)

My question really concerns draging in an outline view, but I'd guess that doesn't make any difference.

If I have two documents open (Same document based application), and I drag an item from one document to another, How can I tell if I'm dropping in a different window than I started in?

The way I would do it off hand, is set a boolean ivar to Yes in the outlineview:writeItems... then set it back to No upon successful drop. Then at entry into outlineView:acceptDrop... the ivar should be Yes if the drop is in the same document, No if it is a different document.

Is there some better, or mor开发者_如何学编程e conventional way that I'm missing?

After all this time, I guess there is no one with a better idea. Seems like this would come up often enough that there should be a standard approach.

I implemented this with a boolean ivar as I described and it works fine.