an NSColor extension to convert CSS style hex string into a color and back

NSColor+HexString.swift

extension NSColor {
    convenience init?(hexString: String) {
        var hexString: String = hexString.trimmingCharacters(in: CharacterSet.whitespacesAndNewlines)
        
        if hexString.hasPrefix("#") {
            let startIndex = hexString.index(hexString.startIndex, offsetBy: 1)
            hexString = String(hexString[startIndex...])
        }
        if hexString.count == 3 || hexString.count == 4 {
            hexString = hexString.reduce(into: "") { (paddedHex, hexCharacter) in
                paddedHex += "\(hexCharacter)\(hexCharacter)"
            }
        }
        
        guard hexString.count == 6 || hexString.count == 8 else {
            return nil
        }
        
        let scanner = Scanner(string: hexString)
        
        var hexNumber: UInt64 = 0
        if scanner.scanHexInt64(&hexNumber) {
            let r, g, b, a: CGFloat
            
            switch hexString.count {
            case 6:
                r = CGFloat((hexNumber & 0xFF0000) >> 16) / 255.0
                g = CGFloat((hexNumber & 0x00FF00) >> 8) / 255.0
                b = CGFloat(hexNumber & 0x0000FF) / 255.0
                a = 1.0
            default: // count == 8
                r = CGFloat((hexNumber & 0xFF000000) >> 24) / 255.0
                g = CGFloat((hexNumber & 0x00FF0000) >> 16) / 255.0
                b = CGFloat((hexNumber & 0x0000FF00) >> 8) / 255.0
                a = CGFloat(hexNumber & 0x000000FF) / 255.0
            }
            
            self.init(red: r, green: g, blue: b, alpha: a)
            return
        }
        
        return nil
    }
    
    func hexString(includingAlpha: Bool = false) -> String {
        var result = String(format: "#%02lX%02lX%02lX", lroundf(Float(redComponent) * 255), lroundf(Float(greenComponent) * 255), lroundf(Float(blueComponent) * 255))
        if (includingAlpha) {
            result += String(format: "%02lX", lroundf(Float(alphaComponent) * 255))
        }
        
        return result
    }
}