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();
}