- (void)prepareForDeletion
{
//    [super prepareForDeletion]; // commented but uncommenting doesn't change results
    [MyDataManager deleteChildOneForMainObject:self];
    [MyDataManager deleteChildrenTwoForMainObject:self];
    [MyDataManager deleteChildrenThreeForMainObject:self];
}

- (BOOL)deleteChildOneForMainObject:(MainObject *)mainObject
{
    NSFetchRequest *fetch = [[NSFetchRequest alloc] init];
    NSEntityDescription *entity = [NSEntityDescription entityForName:@"ChildOne" inManagedObjectContext:managedObjectContext];
    [fetch setEntity:entity];
    [fetch setPredicate:[NSPredicate predicateWithFormat:@"(mainObject == %@)", mainObject]];
    NSError *error;
    NSArray *childOnesToDelete = [managedObjectContext executeFetchRequest:fetch error:&error];
    if (childOnesToDelete.count > 1)
    {
        NSLog(@"[WARNING] More than one ChildOne for mainObject found; deleting all");
    }
    NSLog(@"[TEST] Deleting %i ChildOnes", childOnesToDelete.count);
    for (ChildOne *childOne in childOnesToDelete)
    {
        [managedObjectContext deleteObject:childOne];
    }
    if ([managedObjectContext save:&error]) return YES;
    else NSLog(@"[WARNING] Save error for function [deleteChildOneForMainObject:]");
    return NO;
}