Converting Hex String to NSData in Swift

Question

I got the code to convert String to HEX-String in objective-C.

- (NSString *) CreateDataWithHexString:(NSString*)inputString
{
NSUInteger inLength = [inputSt         


        

Answer 1

Here is my take on converting hexadecimal string to Data using Swift 4:

extension Data {
    private static let hexRegex = try! NSRegularExpression(pattern: "^([a-fA-F0-9][a-fA-F0-9])*$", options: [])

    init?(hexString: String) {
        if Data.hexRegex.matches(in: hexString, range: NSMakeRange(0, hexString.count)).isEmpty {
            return nil // does not look like a hexadecimal string
        }

        let chars = Array(hexString)

        let bytes: [UInt8] = 
            stride(from: 0, to: chars.count, by: 2)
                .map {UInt8(String([chars[$0], chars[$0+1]]), radix: 16)}
                .compactMap{$0}

        self = Data(bytes)
    }

    var hexString: String {
        return map { String(format: "%02hhx", $0) }.joined()
    }
}

(I threw in a small feature for converting back to hex string I found in this answer)

And here is how you would use it:

    let data = Data(hexString: "cafecafe")

    print(data?.hexString) // will print Optional("cafecafe")