Data+HexString.swift

import Foundation

extension Data {

    var hexString1: String {
        return self.map({ return String(format: "%02hhx", $0) }).joined()
    }

    var hexString2: String {
        return self.reduce("", { return $0 + String(format: "%02hhx", $1) })
    }

    var hexString3: String {
        return self.reduce("", { String(format: "\($0)%02hhx", $1) })
    }

}

let token = "test data".data(using: String.Encoding.utf8)!


token.hexString3 == "746573742064617461" // => true