这样写没问题的:
UIImageView *imgView = [UIImageView alloc]initWithFrame:...];
[self.view addsubview imgView];
[imgView release];
UILabel *label = [[UILabel alloc]init...];
[imgView addSubview:label]; //不要以为imgView已经释放了,因为self.view仍保有它哩(若保险起见,你也可以把 [imgView release] 放到下边
[label release];