 <p>You can override <code>-[NSView viewWillMoveToSuperview:]</code> in a custom NSView subclass. This is simply a means for your class to be notified when its position in the view hierarchy is about to change. It doesn't have some deeper meaning other than what its name implies, but you can, of course, harness it to serve various purposes. It's not a method on a delegate or on the view controller, but you can implement such delegation yourself if you want.</p> <p>Also, if your code is moving views around the view hierarchy, it can directly do whatever it wants immediately beforehand, which is also roughly when such a method would be called.</p>