addObserver(_:selector:name:object:suspensionBehavior:)
Adds an entry to the receiver’s dispatch table with a specific observer and suspended-notifications behavior, and optional notification name and sender.
Declaration
func addObserver(_ observer: Any, selector: Selector, name: NSNotification.Name?, object: String?, suspensionBehavior: DistributedNotificationCenter.SuspensionBehavior)Parameters
- observer:
Object registering as an observer. Must not be
nil. - selector:
Selector that specifies the message the receiver sends
notificationObserverto notify it of the notification posting. Must not be0. - name:
The name of the notification for which to register the observer; that is, only notifications with this name are delivered to the observer. When
nil, the notification center doesn’t use a notification’s name to decide whether to deliver it to the observer. - object:
The object whose notifications the observer wants to receive; that is, only notifications sent by this sender are delivered to the observer. When
nil, the notification center doesn’t use a notification’s sender to decide whether to deliver it to the observer. - suspensionBehavior:
Notification posting behavior when notification delivery is suspended.
Discussion
The receiver does not retain notificationObserver. Therefore, you should always send NotificationCenter/removeObserver(_:) or removeObserver(_:name:object:) to the receiver before releasing notificationObserver.