CPDistributedNotificationCenter is class that provides a subset of the functionality found in NSDistributedNotificationCenter on Mac OS X. It allows a process to send notifications globally without knowledge of listening clients. Interested clients can register for distributed notifications from a known server, and these notifications will be posted via the local NSNotificationCenter.
Usage
N.B. A server cannot immediately start posting notifications on creation. Even if a client process starts listening for notifications before the server runs, there is a minor delay incurred due to registration. Notifications sent by the server will only be sent to clients that have resulted in CPDistributedNotificationCenterClientDidStartListeningNotification being posted. A server can optionally watch for this notification (as well as CPDistributedNotificationCenterClientDidStopListeningNotification) and maintain a counter of listening processes. If there are no listening processes, then the server can avoid or defer posting notifications.
Server
-(id)init...
{
...
// Center name must be unique, recommend using application identifier.
CPDistributedNotificationCenter* notificationCenter;
notificationCenter = [CPDistributedNotificationCenter centerNamed:@"unique.name.for.messaging.center.note"];
[notificationCenter runServer]; // or runServerOnCurrentThread on iOS 4.x or earlier
[notificationCenter retain];
// Register to get notified of listening clients
NSNotificationCenter* nc = [NSNotificationCenter defaultCenter];
[nc addObserver:self
selector:@selector(clientDidStartListening:)
name:@"CPDistributedNotificationCenterClientDidStartListeningNotification"
object:notificationCenter];
...
}
- (void)clientDidStartListening:(NSNotification*)note
{
NSDictionary* userInfo = [note userInfo];
CPDistributedNotificationCenter* notificationCenter = [note object];
NSString* bundleIdentifier = [userInfo objectForKey:@"CPBundleIdentifier"];
[notificationCenter postNotificationName:@"notification name"
userInfo:[NSDictionary dictionaryWithObject:@"hello" forKey:@"message"]];
// optionally call with toBundleIdentifier: to only send notification to this client (or any specific client)
}
Client
CPDistributedNotificationCenter* notificationCenter;
notificationCenter = [CPDistributedNotificationCenter centerNamed:@"unique.name.for.messaging.center.note"];
[notificationCenter startDeliveringNotificationsToMainThread];
NSNotificationCenter* nc = [NSNotificationCenter defaultCenter];
[nc addObserver:self
selector:@selector(gotNotification:) // this method will be called whenever the server posts a notification
name:nil // or name of the notification you are interested in
object:nil];
Header
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