字符串与Data的转换

var send: String  = "hello"
let data: Data = send.data(using: .utf8)!

let receive: String = String(data: data, encoding: .utf8)!
print(receive)

Int与Data的转换

var send1: Int = 199
var data1: Data = Data(bytes: &send1, count: 8)

var receive1: Int = 0
(data1 as NSData).getBytes(&receive1, length: 8)
print(receive1)