cocoa - IBOutlet in objective-c

Question

what does this line of code do :

IBOutlet UITextField *userName;

Answer 1

Maybe a little more detailed than changelog, but primarily posting just because I'd already typed it, it may help and it wouldn't format correctly as a comment, not because I disagree with his answer:

IBOutlet is a no-op in code terms. So that declares an instance variable of type UITextField * and with name userName, exactly as if you'd typed just:

UITextField *userName;

What IBOutlet does is flag that member variable up as intended to be used as an outlet in Interface Builder (hence the IB). So when Interface Builder (or Xcode 4, since the two are now integrated) parses your class definition it knows to expose userName as something you can connect to a control.