A
 /
B   C

-(void)contextDidSaveNotification:(NSNotification *)notification
{
    NSManagedObjectContext *context = [notification object];
    if(context!=_moc.parentContext)
        return;
    NSLog(@"Context %@ did save, merging into %@, info:n%@", context, _moc, [notification userInfo]);
    [_moc mergeChangesFromContextDidSaveNotification:notification];
}