[swift3] convert Dictionary to Data, Data to String in swift3

1. Dictionary to Data

let dataExample: Data = NSKeyedArchiver.archivedData(withRootObject: dictionaryExample)

2. Data to Dictionary

let dictionary: Dictionary? = NSKeyedUnarchiver.unarchiveObject(with: dataExample) as! [String : Any]

3. String to Data

var somedata = testString.data(using: String.Encoding.utf8)

4. Data to String

var backToString = String(data: somedata!, encoding: String.Encoding.utf8) as String!

5. JsonString to Data

let jsonData = try JSONSerialization.data(withJSONObject: dic, options: .prettyPrinted)

6. jsonData to Dictionary

    let decoded = try JSONSerialization.jsonObject(with: jsonData, options: [])
    // here "decoded" is of type `Any`, decoded from JSON data

    // you can now cast it with the right type        
    if let dictFromJSON = decoded as? [String:String] {
        // use dictFromJSON
    }