c++ - 成员函数指针错误，boost bind

Question

我在一个没有任何类的文件中编写了一个连接到服务器的客户端。这显然不是一种好的编程方式，所以当代码最终按照我的意愿运行时，我使用以下 client.h 创建了 myclient 类:

    #include <boost/asio.hpp> 
    #include <boost/array.hpp> 
    #include <iostream> 
    #include <string> 
    #include "mtbf.h"
    #include <boost/date_time/posix_time/posix_time.hpp>

    class myclient
    {
    public:
    boost::asio::io_service io_service; 
    boost::asio::ip::tcp::resolver resolver; 
    boost::asio::ip::tcp::socket sock; 
    boost::array<char, 4096> buffer; 
    typedef boost::posix_time::time_duration duration_t;
    typedef boost::posix_time::ptime timestamp_t;
    std::vector<std::string> tokens;
    boost::system::error_code m_err_feedback;



            enum ConnectionState
        {
            WAIT_FOR_HEADER,
            WAIT_FOR_DATA,
            PACKET_COMPLETE
        };
    myclient(std::string port);
    private:
        void read_handler(const boost::system::error_code &ec, std::size_t bytes_transferred);
        void connect_handler(const boost::system::error_code &ec);
        void resolve_handler(const boost::system::error_code &ec, boost::asio::ip::tcp::resolver::iterator it);

    };

我没有写client.cpp的完整代码，但是这里是错误发生的地方(构造函数)

    myclient::myclient(std::string port):resolver(io_service),sock(io_service)
    {
        tcp::resolver::query query("127.0.0.1", port); 
        resolver.async_resolve(query, boost::bind(&myclient::resolve_handler, this)); 
        io_service.run(); 
    }

我是 C++ 的新手，但我知道我需要一个 boost::bind 来调用中的成员函数的引用

 resolver.async_resolve(query, boost::bind(&myclient::resolve_handler, this)); 

但不知何故这不太正确..我得到一个错误:

error   8   error C2298: 'return': Invalid procedure for an expression with pointer to memberfunction C:\projekte\libs\boost_1_53_0-VC11\boost\bind\mem_fn.hpp  342 1   client

编辑:感谢您的回复..但似乎还有更多错误。我错过了一些微不足道的事情吗？这是来自 client.cpp 的代码(我删除了 read_handler 中的实际算法，因为它不重要)

    #include "client.h"
    using boost::asio::ip::tcp;

    myclient::myclient(std::string port):resolver(io_service),sock(io_service)
    {
        tcp::resolver::query query("127.0.0.1", port); 
        resolver.async_resolve(query, boost::bind(&myclient::resolve_handler, this,boost::asio::placeholders::error,boost::asio::placeholders::iterator)); 
        io_service.run(); 
    }

    void myclient::read_handler(const boost::system::error_code &ec, std::size_t bytes_transferred) 
    { 

    .
    .
    .


    } 

    void myclient::connect_handler(const boost::system::error_code &ec) 
    { 
      if (!ec) 
      { 
        sock.async_read_some(boost::asio::buffer(buffer), boost::bind(&myclient::read_handler, this,&ec)); 
      } 
    } 

    void myclient::resolve_handler(const boost::system::error_code &ec, boost::asio::ip::tcp::resolver::iterator it) 
    { 
      if (!ec) 
      { 
        sock.async_connect(*it, boost::bind(&myclient::connect_handler, this, &ec, it)); 
      } 
    } 

有了这个，我得到了这样的错误:

error   2   error C2825: "F": must be a class or namespace "::".    C:\projekte\libs\boost_1_53_0-VC11\boost\bind\bind.hpp  69  1   client
error   3   error C2039: 'result_type': is not an element of '`global namespace''   C:\projekte\libs\boost_1_53_0-VC11\boost\bind\bind.hpp  69  1   client

Answer 1

您忘记了 resolve_handler 参数的占位符:

boost::bind(&myclient::resolve_handler, this,
    boost::asio::placeholders::error, 
    boost::asio::placeholders::iterator)