1、clipsToBounds  默认为NO。代码：

UIView *tmpView = [[UIView alloc] initWithFrame:CGRectMake(0, 0, 320, 200)];
    tmpView.clipsToBounds = YES;//分别设置 YES /NO查看效果
    [self.view addSubview:tmpView];
    UIImageView *imageView = [[UIImageView alloc] initWithImage:[UIImage imageNamed:@"changmen.jpg"]];
    [tmpView addSubview:imageView];

当为NO时：如图

设置为YES，如图

UIView 属性