async 和 future
这个和 C# 的 Task 有点像。
#include <iostream>
#include <string>
#include <memory>
#include <future>
#include <thread>using namespace std;int calculate()
{std::this_thread::sleep_for(std::chrono::seconds(2));return 42;
}class Dog
{
public:int wangWang(){std::this_thread::sleep_for(std::chrono::seconds(3));return 23;}
};int main()
{std::future<int> res = std::async(std::launch::async, calculate);int result = res.get(); // 这里会等待完成cout << result << '\n';Dog dog;res = std::async(std::launch::async, &Dog::wangWang, &dog); // 成员函数int dog_result = res.get();cout << dog_result << '\n';return EXIT_SUCCESS;
}
输出：
42
23
std::packaged_task
#include <iostream>
#include <memory>
#include <future>
using namespace std;int calculate(int x, int y)
{return x + y;
}class Dog
{
public:int calculate(int x, int y){return x + y;}
};int main()
{// 直接绑定函数std::packaged_task<int(int, int)> task(calculate);std::future<int> f_result = task.get_future();std::thread t(std::move(task), 100, 200);t.join();int result = f_result.get();cout << result << '\n';// bind 类成员函数 可调用对象Dog dog;std::function<int(int, int)> func = std::bind(&Dog::calculate, &dog, std::placeholders::_1, std::placeholders::_2);std::packaged_task<int(int, int)> task_1(func);std::future<int> f_result_1 = task_1.get_future();std::thread t_1(std::move(task_1), 10, 20);t_1.join();int result_1 = f_result_1.get();cout << result_1 << '\n';system("pause");return EXIT_SUCCESS;
}
输出：
300
30
promise
能够在某个线程中给它赋值，然后我们可以在其他线程中，把这个取值出来用;
#include <future>
#include <iostream>
int main()
{std::promise<int> p;std::future<int> f = p.get_future();std::thread t([&p](){p.set_value(42);});t.join();int result = f.get();std::cout << result << std::endl; // 输出42system("pause");return EXIT_SUCCESS;
}
参考：http://www.seestudy.cn/?list_9/43.html
