convert dictionary to json serialization swift 4

1let dic = ["2": "B", "1": "A", "3": "C"]
2let encoder = JSONEncoder()
3if let jsonData = try? encoder.encode(dic) {
4    if let jsonString = String(data: jsonData, encoding: .utf8) {
5        print(jsonString)
6    }
7}

1["A":123, "B":455]