Initialize UIColor from HEX value

iOS, Swift

A simple Swift extension to initialize UIColor from a hex string taking into consideration edge cases and hex representation variations

Read the blog post for more details.

extension UIColor {
    convenience init?(hex: String) {
        var hexString = hex
        if hexString.hasPrefix("#") { // Remove the '#' prefix if added.
            let start = hexString.index(hexString.startIndex, offsetBy: 1)
            hexString = String(hexString[start...])
        }
        if hexString.lowercased().hasPrefix("0x") { // Remove the '0x' prefix if added.
            let start = hexString.index(hexString.startIndex, offsetBy: 2)
            hexString = String(hexString[start...])
        }
        let r, g, b, a: CGFloat
        let scanner = Scanner(string: hexString)
        var hexNumber: UInt64 = 0
        guard scanner.scanHexInt64(&hexNumber) else { return nil } // Make sure the strinng is a hex code.
        switch hexString.count {
        case 3, 4: // Color is in short hex format
            var updatedHexString = ""
            hexString.forEach { updatedHexString.append(String(repeating: String($0), count: 2)) }
            hexString = updatedHexString
            self.init(hex: hexString)
        case 6: // Color is in hex format without alpha.
            r = CGFloat((hexNumber & 0xFF0000) >> 16) / 255.0
            g = CGFloat((hexNumber & 0x00FF00) >> 8) / 255.0
            b = CGFloat(hexNumber & 0x0000FF) / 255.0
            a = 1.0
            self.init(red: r, green: g, blue: b, alpha: a)
        case 8: // Color is in hex format with alpha.
            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)
        default: // Invalid format.
            return nil
        }
    }
}