Q. Why do I keep seeing things referred to as NIB/XIB files?
A. The origins of IB trace back to the NeXT Computer, which made use of NIB files to store individual views. These files, in fact, still bore the same name when Mac OS X was released. In recent years, however, Apple renamed the files to have the .xib extension, which has subsequently been mostly replaced by storyboards and scenes. You’ll still see a XIB file used for your startup screen in your project (see Hour 2 for details), but, in general, anything that refers to a XIB or NIB file applies to storyboards as well.
Q. Some of the objects in the IB Object Library can’t be added to my view. What gives?
A. Not all the items in the Object Library are interface objects. Some represent objects that provide functionality to your application. These can be added to the scene in the document outline area or on the icon bar located below a scene’s layout in the IB editor.
Q. I’ve seen controls in applications that aren’t available here. Where are they?
A. Keep in mind that the iOS objects are heavily customizable and frequently used as a starting point for developers to make their own UI classes or subclasses. The end result can vary tremendously from the stock UI appearance.