I prefer the singleton method myself but Apple recommends dependency injection i.e. passing a data model object from view controller to view controller as needed.
If you look at a Core Data utilizing template navigation project in Xcode, you can see how this works. The managedObject context is the data model and it is initialized and held by the app delegate. You can then access it two ways:
(1) Since the Application instances itself is a singleton, you can ask it for its delegate and then ask the delegate for its managedObjectContest property. So, in a view controller you would have a property managedObjectContext with a custom getter defined like:
(NSManagedObjectContext *) managedObjectContext{
if (managedObjectContext !=nil){
return managedObjectContext;
}
// this is basically applicationObject.delegate.managedObjectContext
self.managedObjectContext=[[[NSApplication sharedApplication] delegate] managedObjectContext];
return managedObjectContext
}
(2) Alternatively, whenever a view opens another view, it just sets the next view's managedObjectContext property to it's own. So that every view opens with a context. This is useful if you actually have multiple data objects for some reason.
If your just using an array or a custom data model class just substitute its name for the managedObjectContext in the code above.
