button设置一边圆角

设置一边圆角
缺点：不能设置颜色，正在研究。

typedef NS_ENUM(NSInteger, CNButtonSide) {
    CNButtonSideLeft,
    CNButtonSideRight,
    CNButtonSideUp,
    CNButtonSideDown
};


- (void)roundSide:(CNButtonSide)side
{
    UIBezierPath *maskPath;
    
    if (side == CNButtonSideLeft)
        maskPath = [UIBezierPath bezierPathWithRoundedRect:self.bounds
                                         byRoundingCorners:(UIRectCornerTopLeft|UIRectCornerBottomLeft)
                                               cornerRadii:CGSizeMake(8.f, 8.f)];
    else if (side == CNButtonSideRight)
        maskPath = [UIBezierPath bezierPathWithRoundedRect:self.bounds
                                         byRoundingCorners:(UIRectCornerTopRight|UIRectCornerBottomRight)
                                               cornerRadii:CGSizeMake(8.f, 8.f)];
    else if (side == CNButtonSideUp)
        maskPath = [UIBezierPath bezierPathWithRoundedRect:self.bounds
                                         byRoundingCorners:(UIRectCornerTopLeft|UIRectCornerTopRight)
                                               cornerRadii:CGSizeMake(8.f, 8.f)];
    else
        maskPath = [UIBezierPath bezierPathWithRoundedRect:self.bounds
                                         byRoundingCorners:(UIRectCornerBottomLeft|UIRectCornerBottomRight)
                                               cornerRadii:CGSizeMake(8.f, 8.f)];
    
    // Create the shape layer and set its path
    CAShapeLayer *maskLayer = [CAShapeLayer layer];
    maskLayer.frame = self.bounds;
    maskLayer.path = maskPath.CGPath;
    
    // Set the newly created shape layer as the mask for the image view's layer
    self.layer.mask = maskLayer;
    
    [self.layer setMasksToBounds:YES];
}