iOS: Underline textfield or label

func addUnderline(toTextField textField: DefaultTextField) {
        textField.borderStyle = UITextBorderStyle.none;
        let border = CALayer()
        let borderWidth = CGFloat(1.0)
        border.borderColor = UIColor(red: 91/255.0, green: 92/255.0, blue: 93/255.0, alpha: 1).cgColor
        border.frame = CGRect(x: 0, y: textField.frame.size.height - borderWidth, width: textField.frame.size.width, height: textField.frame.size.height)
        border.borderWidth = borderWidth
        textField.layer.addSublayer(border)
        textField.layer.masksToBounds = true
    }