Hex String to UIColor, both static and dynamic string support

UIColor+Hex.swift

extension UIColor {
    
    convenience init(hex: StaticString) {
        let hex = String(hex.description)

        guard let rgb = UIColor.rgbValue(from: hex) else {
            preconditionFailure("Invalid hex color string provided")
        }

        self.init(
            red: CGFloat((rgb & 0xFF0000) >> 16) / 255.0,
            green: CGFloat((rgb & 0x00FF00) >> 8) / 255.0,
            blue: CGFloat(rgb & 0x0000FF) / 255.0,
            alpha: CGFloat(1.0)
        )
    }
    
    convenience init?(hex: String) {
        let hex = String(hex.description)

        guard let rgb = UIColor.rgbValue(from: hex) else {
            return nil
        }

        self.init(
            red: CGFloat((rgb & 0xFF0000) >> 16) / 255.0,
            green: CGFloat((rgb & 0x00FF00) >> 8) / 255.0,
            blue: CGFloat(rgb & 0x0000FF) / 255.0,
            alpha: CGFloat(1.0)
        )
    }
    
    private static func rgbValue(from hex: String) -> UInt64? {
        var cString: String = hex.trimmingCharacters(in: .whitespacesAndNewlines).uppercased()

        if (cString.hasPrefix("#")) {
            cString.remove(at: cString.startIndex)
        }

        if ((cString.count) != 6) {
            return nil
        }

        var rgbValue: UInt64 = 0
        Scanner(string: cString).scanHexInt64(&rgbValue)
        return rgbValue
    }
}