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# Notifications

Design patterns for broadcasting information and for subscribing to broadcasts.

## Topics

### Key-Value Observing

  <doc://com.apple.documentation/documentation/ObjectiveC/nskeyvalueobserving>

### Notifications

[`Notification`](/documentation/Foundation/Notification)

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

[`NotificationCenter`](/documentation/Foundation/NotificationCenter)

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

[`NotificationQueue`](/documentation/Foundation/NotificationQueue)

A notification center buffer.

### Notifications

[`NSNotification`](/documentation/Foundation/NSNotification)

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

[`NotificationCenter`](/documentation/Foundation/NotificationCenter)

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

[`NotificationQueue`](/documentation/Foundation/NotificationQueue)

A notification center buffer.

### Cross-Process Notifications

[`DistributedNotificationCenter`](/documentation/Foundation/DistributedNotificationCenter)

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


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