C++11 thread 使用类成员变量_c++ thread作为类成员变量-优快云博客

文章目录

看到网上的例子大多是记录如何调用一个外部全局函数接口，
不过，先说明下thread的用法，后续再说明如何使用对象的方式使用thread

get_id: 获取线程 ID

返回一个类型为 std::thread::id 的对象。请看下面例子：

#include <iostream>
#include <thread>
#include <chrono>

void foo()
{
  std::this_thread::sleep_for(std::chrono::seconds(1));
}

int main()
{
  std::thread t1(foo);
  std::thread::id t1_id = t1.get_id();

  std::thread t2(foo);
  std::thread::id t2_id = t2.get_id();

  std::cout << "t1's id: " << t1_id << '\n';
  std::cout << "t2's id: " << t2_id << '\n';

  t1.join();
  t2.join();
}

joinable: 检查线程是否可被 join

检查当前的线程对象是否表示了一个活动的执行线程，由默认构造函数创建的线程是不能被 join 的。另外，如果某个线程已经执行完任务，但是没有被 join 的话，该线程依然会被认为是一个活动的执行线程，因此也是可以被 join 的。

代码如下：

#include <iostream>
#include <thread>
#include <chrono>

void foo()
{
  std::this_thread::sleep_for(std::chrono::seconds(1));
}

int main()
{
  std::thread t;
  std::cout << "before starting, joinable: " << t.joinable() << '\n';

  t = std::thread(foo);
  std::cout << "after starting, joinable: " << t.joinable() << '\n';

  t.join();
}
join: Join 线程，调用该函数会阻塞当前线程，直到由 *this 所标示的线程执行完毕 join 才返回。

#include <iostream>
#include <thread>
#include <chrono>

void foo()
{
  // simulate expensive operation
  std::this_thread::sleep_for(std::chrono::seconds(1));
}

void bar()
{
  // simulate expensive operation
  std::this_thread::sleep_for(std::chrono::seconds(1));
}

int main()
{
  std::cout << "starting first helper...\n";
  std::thread helper1(foo);

  std::cout << "starting second helper...\n";
  std::thread helper2(bar);

  std::cout << "waiting for helpers to finish..." << std::endl;
  helper1.join();
  helper2.join();

  std::cout << "done!\n";
}

detach: Detach线程

将当前线程对象所代表的执行实例与该线程对象分离，使得线程的执行可以单独进行。一旦线程执行完毕，它所分配的资源将会被释放。

调用 detach 函数之后：

*this 不再代表任何的线程执行实例。
joinable() == false
get_id() == std::thread::id()

另外，如果出错或者 joinable() == false，则会抛出 std::system_error。

#include <iostream>
#include <chrono>
#include <thread>
 
void independentThread() 
{
    std::cout << "Starting concurrent thread.\n";
    std::this_thread::sleep_for(std::chrono::seconds(2));
    std::cout << "Exiting concurrent thread.\n";
}
 
void threadCaller() 
{
    std::cout << "Starting thread caller.\n";
    std::thread t(independentThread);
    t.detach();
    std::this_thread::sleep_for(std::chrono::seconds(1));
    std::cout << "Exiting thread caller.\n";
}
 
int main() 
{
    threadCaller();
    std::this_thread::sleep_for(std::chrono::seconds(5));
}

swap: Swap 线程

#include <iostream>
#include <thread>
#include <chrono>

void foo()
{
  std::this_thread::sleep_for(std::chrono::seconds(1));
}

void bar()
{
  std::this_thread::sleep_for(std::chrono::seconds(1));
}

int main()
{
  std::thread t1(foo);
  std::thread t2(bar);

  std::cout << "thread 1 id: " << t1.get_id() << std::endl;
  std::cout << "thread 2 id: " << t2.get_id() << std::endl;

  std::swap(t1, t2);

  std::cout << "after std::swap(t1, t2):" << std::endl;
  std::cout << "thread 1 id: " << t1.get_id() << std::endl;
  std::cout << "thread 2 id: " << t2.get_id() << std::endl;

  t1.swap(t2);

  std::cout << "after t1.swap(t2):" << std::endl;
  std::cout << "thread 1 id: " << t1.get_id() << std::endl;
  std::cout << "thread 2 id: " << t2.get_id() << std::endl;

  t1.join();
  t2.join();
}

执行结果如下：

thread 1 id: 1892
thread 2 id: 2584
after std::swap(t1, t2):
thread 1 id: 2584
thread 2 id: 1892
after t1.swap(t2):
thread 1 id: 1892
thread 2 id: 2584

C++11 thread调用对象的成员函数

如果掉一个类的成员函数，大概是这样。

clientThread = std::thread(&Client::sendMessage,“message”);

std::thread 调用类的成员函数需要传递类的一个对象指针作为参数：

#include <thread>
#include <iostream>

class bar {
public:
  void foo() {
    std::cout << "hello from member function" << std::endl;
  }
};

int main()
{
  std::thread t(&bar::foo, bar());
  ///或者
  ///bar b;
  std::thread t(&bar::foo, &b);
  t.join();
}

如果是在类的成员函数中处理thread，传入 this 即可，如：

std::thread spawn() {
    return std::thread(&blub::test, this);
  }

具体参考：

https://wizardforcel.gitbooks.io/cpp-11-faq/content/77.html