33.promise future多线程通信

 #define _CRT_SECURE_NO_WARNINGS

 #include <iostream>

 #include <thread>

 #include <future>

 #include <string>

 #include <cstdlib>

 using namespace std;

 promise <string>val;//全局通信变量

 void main()

 {

     //字符串相加

     /*string str1("123");

     string str2("34");

     string str3(str1 + str2);

     cout << str3 << endl;*/

     thread th1([]()

     {

         future<string> str = val.get_future();//获取未来状态

         cout << "等待中" << endl;

         //阻塞等待

         cout << str.get() << endl;

     }

     );

     thread th2([]()

     {

         system("pause");

         val.set_value("hello");

     }

     );

     th1.join();

     th2.join();

     cin.get();

 }