
138 9 Chapter 7: The Frameworks of Mac OS X:
Cocoa
Operating
System Services
Foundation operating system services include locks, tasks,
and threads. For most purposes, you can let the frameworks
take care of these for you.
Notifications
Notifications are part of the Cocoa messaging system: One ob-
ject can register its interest in another object and certain
events. An object posts a notification when it does something;
Cocoa takes care that the appropriate other objects are noti-
fied.
Notifications are used for such events as window movement
or resizing, application launching or activating, and the like.
What is important about notifications ...