boost :: deadline_timer :: async_wait不是异步的 [英] boost::deadline_timer::async_wait is not asynchronous

问题描述

我执行一个简单的示例作为测试，我想在5秒钟后执行一个简单的操作.我正在使用带有async_wait的boost :: deadline_timer，但async_wait不会异步等待...这是代码:

I execute a simple example as a test, I want execute a simple operation after 5 seconds. I am using the boost::deadline_timer with async_wait, but async_wait not wait asynchronously... This is the code:

void print(const boost::system::error_code& /*e*/)
{
  std::cout << "Second Message\n";
}

int main()
{
  boost::asio::io_service io;

  boost::asio::deadline_timer t(io, boost::posix_time::seconds(5));
  t.async_wait(print);
  io.run();
  std::cout << "First Message\n";
  return 0;
}

这是输出:

Second Message
First Message

有一个错误，因为计时器必须在后台等待，这样才能继续执行下一条指令"cout<< FirstMessage \ n";"

There is an error because, the timer would have to wait in background and so to continue the execution of next instruction that is "cout<<"FirstMessage\n";"

预期的行为是打印第一条消息"，然后打印第二条消息"

The expected behavior is print "First Message" and after print "Second Message"

谢谢，我是这样解决的:

Thanks, I solved in this way:

    boost::asio::io_service io;
    boost::asio::deadline_timer t(io, boost::posix_time::seconds(5));
    t.async_wait(print);
    std::thread thread([&]{io.run();});

推荐答案

io.run()仅在其所有作业完成时退出.尝试安排两个具有不同超时时间的 deadline_times ，然后看看会发生什么.(或将io.run()放入另一个线程.)

io.run() exits only when all its jobs are complete. Try scheduling two deadline_times with different timeouts and see what happens. (Or put the io.run() into another thread.)

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