c++ - 如何从std::thread返回值

Question

我有返回值的函数。我想将线程用于doSth函数，并为上述变量设置返回值，这是一个示例:

#include <string>
#include <iostream>
#include <thread>

using namespace std;

// func for execution
int doSth(int number)
{
    return number;
}

int main()
{
    // some code ...
    int numberOne; // no value now, but in thread I want to set a value from it
    int numberTwo; // depending on function input value
    thread t1(doSth, 1); // set numberOne = 1;
    thread t2(doSth, 2); // set numberTwo = 2;
    // wait them to execute
    t1.join();
    t2.join();
    // now I should have numberOne = 1; numberTwo = 2
    // some code ...
    return 0;
}

我该怎么办？

Answer 1

How to return value from std::thread

除了其他答案中显示的 std::async之外，您还可以使用 std::packaged_task:

std::packaged_task<int(int)> task{doSth};
std::future<int> result = task.get_future();
task(1);
int numberOne = result.get();

这允许分离任务的创建，并在需要时执行它。