NSString转化为NSData

var string1 = "This is some string"
var nsdata = string1.data(using: String.Encoding.utf8)//NSData 类型

NSData转化为 NSString

            let loaclData   //这是一段NSdata数据
            let str2 = String(data: loaclData, encoding: String.Encoding.utf8)!
            print("转化的结果是\(str2)")