前言：ios开发中经常遇到一个view上只要两个圆角的情况。
1.切四个圆角的情况

view.layer.cornerRadius = 12;
view.layer.masksToBounds = YES;

2.单独切圆角的情况，比如切左上、右上两个圆角

 UIBezierPath *maskPath = [UIBezierPath bezierPathWithRoundedRect:CGRectMake(0, 0, SCREEN_WIDTH, 1000) byRoundingCorners:UIRectCornerTopLeft | UIRectCornerTopRight cornerRadii:CGSizeMake(12, 12)];
 CAShapeLayer *maskLayer = [[CAShapeLayer alloc] init];
 maskLayer.frame = self.bottomView.bounds;
 maskLayer.path = maskPath.CGPath;
 self.bottomView.layer.mask = maskLayer;

解决！
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