IBOutlet and IBAction

You have already used IBOutlets and IBActions in previous chapters. Without really knowing what they are, you probably already have a good idea of what they accomplish; outlets and actions are how you connect things in a nib with things outside a nib. An outlet connects an instance variable outside a nib to an object in a nib.

IBOutlet is a preprocessor directive, evaluates to void, and is ignored by the compiler, but all you really need to know is that IBOutlet is how Interface Builder knows the variable was created for its use. When you change the class of an object, Interface Builder scans the class for IBOutlets and knows those variables are intended as outlets. You can then easily connect your graphical component to the variable, as Interface Builder adds the outlets to the inspector automatically for you to select. Note, though, Interface Builder doesn’t connect the outlets to anything; it just adds them. You are responsible for adding any connections.