do{
let json = try JSONSerialization.jsonObject(with: data!, options: []) as? [String : Any]
}catch{ print("erroMsg") }

 let jsonText = "{\"first_name\":\"Sergey\"}" var dictonary:NSDictionary? if let data = jsonText.data(using: String.Encoding.utf8) { do { dictonary = try JSONSerialization.jsonObject(with: data, options: []) as? [String:AnyObject] if let myDictionary = dictonary { print(" First name is: \(myDictionary["first_name"]!)") } } catch let error as NSError { print(error) } }

struct Sentence : Codable { let sentence : String let lang : String
}
let sentences = [Sentence(sentence: "Hello world", lang: "en"), Sentence(sentence: "Hallo Welt", lang: "de")]
do { let jsonData = try JSONEncoder().encode(sentences) let jsonString = String(data: jsonData, encoding: .utf8)! print(jsonString) // [{"sentence":"Hello world","lang":"en"},{"sentence":"Hallo Welt","lang":"de"}] // and decode it back let decodedSentences = try JSONDecoder().decode([Sentence].self, from: jsonData) print(decodedSentences)
} catch { print(error) }

func jsonToString(json: AnyObject){ do { let data1 = try NSJSONSerialization.dataWithJSONObject(json, options: NSJSONWritingOptions.PrettyPrinted) // first of all convert json to the data let convertedString = String(data: data1, encoding: NSUTF8StringEncoding) // the data will be converted to the string print(convertedString) // <-- here is ur string } catch let myJSONError { print(myJSONError) } }