c++多线程（十 三） - std::promise

std::promise 是类模板 ，可以在某个线程中给它赋值，然后在其他线程中取值。

#include<iostream>
#include<future>
using namespace std;

void myThread(std::promise<int> &temp, int num)
{
	cout << "Thread start id = " << this_thread::get_id() << endl;
	chrono::milliseconds time(5000);  //休息5秒
	this_thread::sleep_for(time);
	temp.set_value(num *2);           //将结果保存在promise对象中
	cout << "Thread end id = " << this_thread::get_id() << endl;	
}

int main()
{
	cout << "Main start id = " << this_thread::get_id() << endl;
	promise<int> promise;             //promise对象中保存值类型为int
	thread thread(myThread, ref(promise),5);
	thread.join();
	future<int> result = promise.get_future();   //获取结果值
	cout << "result = " << result.get() << endl;
	return 0;
}

执行结果：