Design patterns for broadcasting information and for subscribing to broadcasts.


Key-Value Observing


An informal protocol that objects adopt to be notified of changes to the specified properties of other objects.


struct Notification

A container for information broadcast through a notification center to all registered observers.

class NotificationCenter

A notification dispatch mechanism that enables the broadcast of information to registered observers.

class NotificationQueue

A notification center buffer.

Cross-Process Notifications

class DistributedNotificationCenter

A notification dispatch mechanism that enables the broadcast of notifications across task boundaries.

See Also

App Support

Task Management

Manage your app’s work and how it interacts with system services like Handoff and Shortcuts.


Access assets and other data bundled with your app.

App Extension Support

Manage the interaction between an app extension and its hosting app.

Errors and Exceptions

Respond to problem situations in your interactions with APIs, and fine-tune your app for better debugging.

Scripting Support

Allow users to control your app with AppleScript and other automation technologies, or run scripts from within your app.