How to use hex color values in Swift

extension UIColor {
    public convenience init?(hex: String) {
        let r, g, b, a: CGFloat
        
        guard hex.hasPrefix("#") else {
            return nil
        }
        
        let hexValue = hex.replacingOccurrences(of: "#", with: "")
        guard hexColor.count == 8 else {
            return
        }
        let scanner = Scanner(string: hexValue)
        var hexNumber: UInt64 = 0
        
        guard scanner.scanHexInt64(&hexNumber) else {
            return nil
        }
        r = CGFloat((hexNumber & 0xff000000) >> 24) / 255
        g = CGFloat((hexNumber & 0x00ff0000) >> 16) / 255
        b = CGFloat((hexNumber & 0x0000ff00) >> 8) / 255
        a = CGFloat(hexNumber & 0x000000ff) / 255
        
        self.init(red: r, green: g, blue: b, alpha: a)
        return
    }
}