【Swift】UIColorとHexの相互変換

extension UIColor {
    
    class func hex (_ hexStr : String, alpha : CGFloat) -> UIColor {
        var hexStr = hexStr
        let alpha = alpha
        hexStr = hexStr.replacingOccurrences(of: "#", with: "")
        let scanner = Scanner(string: hexStr)
        var color: UInt64 = 0
        if scanner.scanHexInt64(&color) {
            let r = CGFloat((color & 0xFF0000) >> 16) / 255.0
            let g = CGFloat((color & 0x00FF00) >> 8) / 255.0
            let b = CGFloat(color & 0x0000FF) / 255.0
            return UIColor(red:r,green:g,blue:b,alpha:alpha)
        } else {
            print("不正な値")
            return UIColor.white
        }
    }
    
    func toHex(alpha: Bool = false) -> String {
        guard let components = cgColor.components, components.count >= 3 else {
            return "ffffff"
        }

        let r = Float(components[0])
        let g = Float(components[1])
        let b = Float(components[2])
        var a = Float(1.0)

        if components.count >= 4 {
            a = Float(components[3])
        }

        if alpha {
            return String(format: "%02lX%02lX%02lX%02lX", lroundf(r * 255), lroundf(g * 255), lroundf(b * 255), lroundf(a * 255))
        } else {
            return String(format: "%02lX%02lX%02lX", lroundf(r * 255), lroundf(g * 255), lroundf(b * 255))
        }
    }
}

let color1 = UIColor.hex("00ff00", alpha: 1)
let color2 = UIColor.hex("cccccc", alpha: 1)

let hex1 = color1.toHex()　//00FF00
let hex2 = color2.toHex()　//CCCCCC