DRNotificationCenter

Overview

A DRNotificationCenter object (or simply, notification center) is essentially a notification dispatch table. It notifies all observers of notifications meeting specific criteria. This information is encapsulated in NSNotification objects, also known as notifications. Client objects register themselves with the notification center as observers of specific notifications posted by DiscRecording. When an event occurs, DiscRecording posts an appropriate notification to the notification center. The notification center dispatches a message to each registered observer, passing the notification as the sole argument.

There are two main differences between a DRNotificationCenter and the NSNotificationCenter from Foundation. First is that only Disc Recording posts notifications received through this mechanism. You use this to obtain device plug/unplug events, burn status, etc. Second, there can be multple notification centers active at once. Each run loop of your application will have it's own notification center and notifications from that notification center will be posted to the runloop it was created on.

Methods

-addObserver:selector:name:object:

Adds an observer to the receiver.

+currentRunLoopCenter

Creates an initializes a DRNotificationCenter

-removeObserver:name:object:

Removes anObserver from receiving notifications.

Adds an observer to the receiver.

- (void)addObserver:(id)observer selector:(SEL)aSelector 
        name:(NSString *)notificationName object:(id)anObject; 

Parameters

observer

The observer to send notifications to.

aSelector

The selector to call

notificationName

The notification to listen for

anObject

The object to limit notifications for.

Discussion

Registers anObserver to receive notifications with the name notificationName and/or containing anObject. When a notification of name notificationName containing the object anObject is posted, anObserver receives an aSelector message with this notification as the argument. The method for the selector specified in aSelector must have one and only one argument. If notificationName is nil, the notification center notifies the observer of all notifications with an object matching anObject. If anObject is nil, the notification center notifies the observer of all notifications with the name notificationName.

The notification center does not retain anObserver or anObject. Therefore, you should always send removeObserver:name:object: to the notification center before releasing these objects.

Creates an initializes a DRNotificationCenter

+ (DRNotificationCenter*) currentRunLoopCenter; 

Return Value

A shared DRNotificationCenter object.

Discussion

The instance returned sends Disc Recording notifications only to the current run loop. If you want to receive notifications on another run loop, this method must be called from that runloop.

Removes anObserver from receiving notifications.

- (void)removeObserver:(id)observer name:(NSString *)aName 
        object:(id)anObject; 

Parameters

observer

The observer to remove

aName

The notification the remove the observer from.

anObject

The object the observer was listening for.

Discussion

Removes anObserver as the observer of notifications with the name notificationName and object anObject from the receiver. Be sure to invoke this method before deallocating the observer object or any object specified in addObserver:selector:name:object: .

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Last Updated: 2008-04-01