ios – 在主视图层上方添加子视图

我试图附加图像来显示我的意思,但我没有足够的声誉,所以这里是图像的链接：

http://imageshack.us/photo/my-images/843/img0219u.png/

子视图的一部分被父视图边框遮挡.

如何使子视图显示在父视图层的顶部？

任何帮助表示赞赏.

如果有帮助,这是我的代码：

添加图层的代码：

UIView *student = [[UIView alloc] initWithFrame:CGRectMake(50,50,100,100)];
    student.backgroundColor = [UIColor grayColor];

    CALayer *studentLayer = [[CALayer alloc] init];
    studentLayer.borderColor = [UIColor grayColor].CGColor;
    studentLayer.borderWidth = 5;

    student.layer.borderColor = studentLayer.borderColor;
    student.layer.borderWidth = studentLayer.borderWidth;

添加子视图的代码：

UILabel *ilp = [[UILabel alloc] initWithFrame:(CGRectMake(-20,-10,40,20))];
    ilp.text = @"ILP";
    ilp.backgroundColor = [UIColor yellowColor];
    ilp.textColor = [UIColor blackColor];
    ilp.textAlignment = NSTextAlignmentCenter;

    [student addSubview:ilp];