1. 线程的移动语义实现
基于前面几章介绍的移动语义，我们用它来实现线程。#include <iostream>
#include <thread>
#include <vector>
#include <algorithm>
#include <cassert>
int main()
{
std::vector<std::thread> workers;
for (int i = 0; i < 5; i++) {
auto t = std::thread([i]()
{
std::cout << "thread function: " << i << "\n";
});
workers.push_back(std::move(t));
}
std::cout << "main thread\n";
std::for_each(workers.begin(), workers.end(), [](std::thread &t)
{
assert(t.joinable());
t.join();
});
return 0;
} 运行结果为：thread function: thread function: thread function: 01
thread function: 3
2
main thread
thread function: 4
接下来对代码进行一些改变。将线程函数task()独立出来。
#include <iostream>
#include <thread>
#include <vector>
#include <algorithm>
#include <cassert>
void task(int i)
{
std::cout<<"worker : "<<i<<std::endl;
}
int main()
{
std::vector<std::thread> workers;
for (int i = 0; i < 5; i++) {
auto t = std::thread(&task, i);
workers.push_back(std::move(t));
}
std::cout << "main thread" << std::endl;
std::for_each(workers.begin(), workers.end(), [](std::thread &t)
{
assert(t.joinable());
t.join();
});
return 0;
} 运行结果为：worker : worker : 02
worker : 3
worker : 1
main thread
worker : 4
2. 通过引用传递线程参数
下面将线程函数的参数改为引用void task(int &i)
{
std::cout << "worker : " << i << "\n";
} 与此同时，线程的构造函数同样需要相应的修改auto t = std::thread(&task, std::ref(i));
但是，上面程序看似可以工作，不过不是一个好的设计，因为多个线程在同时使用一个指向相同对象的引用。