CGRect rect = CGRectMake(50, 200, 100, 100);
    CGSize radii = CGSizeMake(5, 5);
//    UIRectCorner corners = UIRectCornerTopRight | UIRectCornerBottomRight | UIRectCornerBottomLeft;
    UIRectCorner corners = UIRectCornerBottomLeft | UIRectCornerBottomRight ;

    //create path
    UIBezierPath *path = [UIBezierPath bezierPathWithRoundedRect:rect byRoundingCorners:corners cornerRadii:radii];
    
    CAShapeLayer *shapeLayer = [CAShapeLayer layer];
    shapeLayer.strokeColor = [UIColor redColor].CGColor;
    shapeLayer.fillColor = [UIColor grayColor].CGColor;
    shapeLayer.lineWidth = 1;
    //线条之间
    shapeLayer.lineJoin = kCALineJoinRound;
    //线条结尾
    shapeLayer.lineCap = kCALineCapRound;
    shapeLayer.path = path.CGPath;
    //add it to our view
    [self.view.layer addSublayer:shapeLayer];

效果如下