Cocoa® Programming Developer’s Handbook, Second Edition

Chapter 5. Application Concepts

An application, in Cocoa terminology, is a process that displays a graphical user interface and runs in an interactive mode. While the Foundation library provides classes that are likely to be useful for any kind of program, AppKit is focused on producing interactive GUIs. A lot of the core functionality for building applications is found in Foundation and extended in AppKit.

5.1 Run Loops

The core of any Cocoa application is the run loop. This provides a simple implementation of coroutines. Each iteration through the run loop is triggered by an event. Handlers for this event are then triggered and run until completion.

The mapping between events and their handlers is rarely explicit in Cocoa. For events triggered ...