The type qualifier IBOutlet is a tag applied to an instance-variable declaration so that the Interface Builder application can recognize the instance variable as an outlet and synchronize the display and connection of it with Xcode.
An outlet is an object instance variable — that is, an instance variable of an object that references another object. With outlets, the reference is configured and archived through Interface Builder. The connections between the containing object and its outlets are reestablished every time the containing object is unarchived from its nib file. The containing object holds an outlet as an instance variable with the type qualifier of IBOutlet.
Example:
IBOutlet NSArray *keywords;
Because it is an instance variable, an outlet becomes part of an object’s encapsulated data. But an outlet is more than a simple instance variable. The connection between an object and its outlets is archived in a nib file; when the nib file is loaded, each connection is unarchived and reestablished, and is thus always available whenever it becomes necessary to send messages to the other object. The type qualifier IBOutlet is a tag applied to an instance-variable declaration so that the Interface Builder application can recognize the instance variable as an outlet and synchronize the display and connection of it with Xcode.
