layer.cornerRadius for left only

gistfile1.m

UIBezierPath *maskPath = [UIBezierPath bezierPathWithRoundedRect:_toggle.bounds
                                               byRoundingCorners:(UIRectCornerTopLeft | UIRectCornerBottomLeft)
                                                     cornerRadii:CGSizeMake(8.0, 8.0)];
CAShapeLayer *maskLayer = [CAShapeLayer new];
maskLayer.frame = _toggle.bounds;
maskLayer.path = maskPath.CGPath;
_toggle.layer.mask = maskLayer;