Checking if NSSet is Populated.

- (void)syncKVO:(NSNotification *)notification {
    NSDictionary *userInfoDictionary = [notification userInfo];
    NSSet *deletedObjects = [userInfoDictionary objectForKey:NSDeletedObjectsKey];
    NSSet *changedObjects = [userInfoDictionary objectForKey:NSUpdatedObjectsKey];

    if ([deletedObjects count]) {
          //do something if it contains objects
    } else {
          if ([changedObjects count]) {
               //do something if it contains objects
          } else {
               //do something if it doesn't contain objects.
          }
    }
}