c++ - boost::bind 与成员函数(作为 boost::asio 异步写处理程序)

Question

我正在使用 boost::bind 将处理函数传递给 boost::asio::async_write。当我使用自由函数时，它工作正常，但是当我尝试将函数移动到一个类中时，绑定(bind)会产生我无法破译的错误。

什么有效:

我写了一些数据:

boost::asio::async_write(*socket,
                         boost::asio::buffer(data(),
                                             length()),
                         boost::bind(handlermessagewrite,
                                     boost::asio::placeholders::error,
                                     this,
                                     boost::asio::placeholders::bytes_transferred));

然后我使用签名为的自由函数处理写入:

void handlermessagewrite(const boost::system::error_code& errorcode,
                         iodata *msg,
                         size_t bytes_transferred);

这一切都按预期工作。

我正在尝试做的事情:

我正在将处理程序移动到类 ioclient 中:

class ioclient {
public:
  void handlermessagewrite(const boost::system::error_code& errorcode,
                           iodata *msg,
                           size_t bytes_transferred);
}

void ioclient::handlermessagewrite(const boost::system::error_code& errorcode,
                                   iodata *msg,
                                   size_t bytes_transferred);

并相应地调整 boost::bind 代码，如官方 asio 教程中所示:

- boost::bind(handlermessagewrite,

+ boost::bind(&ioclient::handlermessagewrite,

但是，这会产生一些极其不透明的编译错误，其中一行似乎最终在我的 IDE 中被截断(code::blocks)这一事实无济于事:

\boost\bind\bind_template.hpp|102| required from 'boost::_bi::bind_t::result_type boost::_bi::bind_t::operator()(const A1&, const A2&) [with A1 = boost::system::error_code; A2 = unsigned int; R = void; F = boost::_mfi::mf2; L = boost::_bi::list3 (*)(), boost::_bi::value, boost::arg<2> (*)()>; boost::_bi::bind_t::result_type = void]'| \boost\asio\impl\write.hpp|261| required from 'void boost::asio::detail::write_op::operator()(const boost::system::error_code&, std::size_t, int) [with AsyncWriteStream = boost::asio::basic_stream_socket; CompletionCondition = boost::asio::detail::transfer_all_t; WriteHandler = boost::_bi::bind_t, boost::_bi::list3 (*)(), boost::_bi::va| \boost\asio\impl\write.hpp|585| required from 'void boost::asio::async_write(AsyncWriteStream&, const ConstBufferSequence&, WriteHandler&&) [with AsyncWriteStream = boost::asio::basic_stream_socket; ConstBufferSequence = boost::asio::mutable_buffers_1; WriteHandler = boost::_bi::bind_t, boost::_bi::list3 (*)(), boost::_bi::value, boost::arg<2> (*)()> >]'| \iodata.cpp|76| required from here| \boost\bind\bind.hpp|392|error: no match for call to '(boost::_mfi::mf2) (const boost::system::error_code&, iodata*&, const unsigned int&)'| \boost\bind\mem_fn_template.hpp|253|note: candidates are:| \boost\bind\mem_fn_template.hpp|278|note: R boost::_mfi::mf2::operator()(T*, A1, A2) const [with R = void; T = ioclient; A1 = const boost::system::error_code&; A2 = iodata*]| \boost\bind\mem_fn_template.hpp|278|note: no known conversion for argument 1 from 'const boost::system::error_code' to 'ioclient*'| \boost\bind\mem_fn_template.hpp|283|note: template R boost::_mfi::mf2::operator()(U&, A1, A2) const [with U = U; R = void; T = ioclient; A1 = const boost::system::error_code&; A2 = iodata*]| \boost\bind\mem_fn_template.hpp|283|note: template argument deduction/substitution failed:| \boost\bind\bind.hpp|392|note: cannot convert '(& a)->boost::_bi::list2::operator[]((* &((boost::_bi::list3 (*)(), boost::_bi::value, boost::arg<2> ()()>)this)->boost::_bi::list3 (*)(), boost::_bi::value, boost::arg<2> (*)()>::.boost::_bi::storage3 (*)(), boost::_bi::value, boost::arg<2> (*)()>::.boost::_bi::storage2 (*)(), boost::bi::value >::a2))' (type 'iodata*') to type 'const boost::system::| \boost\bind\mem_fn_template.hpp|291|note: template R boost::_mfi::mf2::operator()(const U&, A1, A2) const [with U = U; R = void; T = ioclient; A1 = const boost::system::error_code&; A2 = iodata*]| \boost\bind\mem_fn_template.hpp|291|note: template argument deduction/substitution failed:| \boost\bind\bind.hpp|392|note: cannot convert '(& a)->boost::_bi::list2::operator[]((* &((boost::_bi::list3 (*)(), boost::_bi::value, boost::arg<2> ()()>)this)->boost::_bi::list3 (*)(), boost::_bi::value, boost::arg<2> (*)()>::.boost::_bi::storage3 (*)(), boost::_bi::value, boost::arg<2> (*)()>::.boost::_bi::storage2 (*)(), boost::bi::value >::a2))' (type 'iodata*') to type 'const boost::system::| \boost\bind\mem_fn_template.hpp|299|note: R boost::_mfi::mf2::operator()(T&, A1, A2) const [with R = void; T = ioclient; A1 = const boost::system::error_code&; A2 = iodata*]| \boost\bind\mem_fn_template.hpp|299|note: no known conversion for argument 1 from 'const boost::system::error_code' to 'ioclient&'|

我确信我在使用 bind 时做错了什么，但我不知道那可能是什么。有什么想法吗？

Answer 1

使用实例方法时，必须将 this 指针作为第二个参数传递给 bind()。

编辑:

我已经完成了你想用 boost::asio 做的事情。这是我的实现的一个片段:

        boost::asio::async_write(
            m_Socket,
            boost::asio::buffer((const unsigned char *)(rMsg.c_str()), rMsg.length()),
            boost::bind(&ServerToClientConnT::HandleAsioWrite,
                        this,
                        boost::asio::placeholders::error,
                        boost::asio::placeholders::bytes_transferred));

其中 HandleAsioWrite 是如下声明的方法:

void HandleAsioWrite(const boost::system::error_code& rErrorCode,
                     std::size_t nBytesTransferred);