Question

我正在尝试创建一个简单的vector::size类，它包含void get_student_data(vector<student>& v) { for (size_t i = 0; i < v.size(); i++) { cout << "Enter Name of " << (i+1) <<"th student\n"; cin >> v[i].name; } }的基本功能，例如BoostTimer和deadline_timer，以便我的程序只调用async_wait和cancel，我写了以下代码

boosttimer.h

startTimer

boosttimer.cpp

killTimer

timertest.cpp

#ifndef __BOOST_TIMER__
#define __BOOST_TIMER__

#include <boost/asio.hpp>
#include <boost/bind.hpp>
#include <boost/function.hpp>
#include <boost/chrono.hpp>
#include <boost/chrono/duration.hpp>
#include <boost/function.hpp>

class BoostTimer{
public:
        typedef boost::asio::deadline_timer deadline_timer;
        typedef deadline_timer::duration_type duration;
        typedef boost::function<void (boost::system::error_code, BoostTimer&)> handler_function;

        BoostTimer(boost::asio::io_service& io_service, duration interval, handler_function handler);
        ~BoostTimer();

        void startTimer();
        void killTimer();

private:
        deadline_timer _timer;
        boost::asio::io_service& _ioService;
        duration _interval;
        handler_function _handler;
};
#endif

我的问题是如何从我的#include "boosttimer.h" BoostTimer::BoostTimer(boost::asio::io_service& io_service, duration interval, handler_function handler) : _timer(io_service), _ioService(io_service), _interval(interval), _handler(handler) { } BoostTimer::~BoostTimer() { } void BoostTimer::startTimer() { _timer.expires_from_now(_interval); _timer.async_wait(boost::bind(_handler, boost::asio::placeholders::error, boost::ref(*this))); //trying to pass placeholder argument but somehow it doesn't work } void BoostTimer::killTimer() { _timer.cancel(); }班级#include <iostream> #include <boost/asio.hpp> #include "boosttimer.h" //void timer_handler(const boost::system::error_code& /*e*/) // not able to take parameters void timer_handler() //it runs fine without parameters { std::cout<<"timer function has been called" << std::endl; } int main(int argc, char* argv[]) { boost::asio::io_service io_service; BoostTimer timer(io_service,boost::posix_time::seconds(5), boost::bind(&timer_handler)); timer.startTimer(); io_service.run(); return 0; }函数中将参数传递给我的处理函数？我尝试了但是我错过了一些东西。

Answer 1

如果您只想传递来自调用者的参数：

void timer_handler(std::string const& arg1, int arg2)
{
    std::cout<<"timer function has been called with arg1='" << arg1 <<"', arg2=" << arg2 << std::endl;
}

int main()
{

    boost::asio::io_service io_service;
    BoostTimer timer(io_service,boost::posix_time::seconds(5), boost::bind(&timer_handler, "This is arg1", 42));
    timer.startTimer();

    io_service.run();
    return 0;
}

看到 Live On Coliru ，输出：

timer function has been called with arg1='This is arg1', arg2=42

还要传递ec和*this：

CAVEAT 我认为这严重打破了任何封装，并使整个班级基本上多余。考虑在取消时不要调用完成处理程序，例如此外，让调用者绑定它需要的对象实例（对于用户定义的处理程序而言，它需要引用BoostTimer - 这是错误方向的紧密耦合）

void timer_handler(boost::system::error_code ec, BoostTimer& instance, std::string const& arg1, int arg2) //it runs fine without parameters 
{
    std::cout<<"timer function has been called with arg1='" << arg1 <<"', arg2=" << arg2 << " (" << ec.message() << ")\n";
}

int main()
{
    boost::asio::io_service io_service;
    BoostTimer timer(io_service,boost::posix_time::seconds(1), boost::bind(&timer_handler, _1, _2, "This is arg1", 42));
    timer.startTimer();

    io_service.run();
    return 0;
}

同时查看 Live On Coliru ，输出：

timer function has been called with arg1='This is arg1', arg2=42 (Success)

在boost :: deadline_timer上创建包装器，无法将参数传递给处理函数

boosttimer.h

boosttimer.cpp

timertest.cpp

1 个答案: