Singleton Entity in CoreData

Question

I may have the wrong terminology in the title using the word singleton. Now I am looking for a good technique. I have an object called user that stores registered users, such as a session key for server requests. I just want one of these entities to ever exist. Is there a standard technique for this?

That i still have something like this

NSManagedObjectContext *moc = [self managedObjectContext]; NSEntityDescription *entityDescription = [NSEntityDescription entityForName:@"UserEntity" inManagedObjectContext:moc]; NSFetchRequest *request = [[[NSFetchRequest alloc] init] autorelease]; [request setEntity:entityDescription]; NSArray *array = [moc executeFetchRequest:request error:&error]; if (array == nil) { // Deal with error... } if ([array count]==0) { //first run of app }else if([array count]==1) { // id like the code to enter here after every app run except for the first one }else { //dont want this to happen } 

Answer 1

I use the Matt Gallagher approach described in his article Singletons, AppDelegates, and Top-Level Data .

It uses a macro to create a “synthesized singleton” class, which can then be retrieved from anywhere. Very handy for things like sessions, managed object contexts, etc. Otherwise, you will have to go through these rounds everywhere.

Answer 2

Your approach should work, and it can be flexible. Consider the possibility that in a future version of your application it is possible to manage multiple accounts; you can easily achieve this if you model your singleton as a regular object.

If you are 100% sure you will never want this, you can use the metadata repository property to store things like this.