关于clipsTobounds的属性，简单了解。
1.首先UIView的clipsTobounds的SDK中的描述
@property(nonatomic) BOOL clipsToBounds; // When YES, content and subviews are clipped to the bounds of the view. Default is NO.
2.Clip的意思是剪裁，bounds的意思是自身的边界，所以描述的意思：如果clipsToBounds的值是YES,那么子视图内容范围超出父视图的边界，超出的部分就会被剪裁掉
- (void)viewDidLoad {
[super viewDidLoad];
//黑色View
UIView *blackView = [UIView new];
greenView.frame = CGRectMake(0, 0, 250, 250);
greenView.backgroundColor = [UIColor blackColor];
greenView.center = self.view.center;
greenView.clipsToBounds = YES;
[self.view addSubview:greenView];
//红色View
UIView *redView = [UIView new];
redView.frame = CGRectMake(0, 0, 100, 400);
redView.backgroundColor = [UIColor redColor];
redView.center = self.view.center;
[greenView addSubview:redView];}
红色View添加到黑色View上,红色View超出黑色View的部分被剪裁掉
