使用boost：：signal 2：：signal作为处理程序时出错

Question

在以下代码中：

   boost::signals2::signal<void(const boost::system::error_code&)> signal;
   socket.async_connect(endpoint, boost::ref(signal));

(在http://liveworkspace.org/code/e04910cbcc4cfd9e42e34d1af55c393e发现)

我知道这个错误：

文件中包含的

：20，boost/asio/basic_io_object.hpp:20，boost/asio/basic_socket.hpp:19，boost/asio/basic_datagram_socket.hpp:20，boost/asio.hpp:20，boost/asio/basic_Socket.hpp:19，boost/asio/basic_datagram_socket.hpp:20，boost/asio.hpp:20，来自source.cpp:2: boost/asio/detail/bind_handler.hpp:在成员函数'void boost::asio::detail::binder1< boost::reference_wrapper >中，boost::system::error_code ::operator()()'：boost/asio/handler_invoke_hook.hpp:64:3:从'void boost::asio::asio_handler_invoke( boost::asio::detail::binder1< boost::reference_wrapper > )实例化boost::system::error_code，)‘boost/asio/detail/handler_invoke_helpers.hpp:39:3:从'void boost_asio_handler_invoke_helpers::invoke( const boost::asio::detail::binder1< boost::reference_wrapper >，boost::system::error_code &，boost::reference_wrapper >& )‘boost/asio/detail/bind_handler.hpp:73:3:实例化从'void：：asio ::asio_handler_invoke( const boost::asio::detail::binder1< boost::reference_wrapper >，boost::system::error_code &，boost::asio::detail::binder1< boost::reference_wrapper >，boost/asio/detail/handler_invoke_helpers.hpp:39:3:实例化自'void boost_asio_handler_invoke_helpers::invoke( const boost::asio::detail::binder1< boost::reference_wrapper >，boost::system::error_code &，boost::asio::detail::binder1< boost::reference_wrapper >，boost/asio/detail/completion_handler.hpp:63:7:实例化自静态空洞boost：：boost::system::error_code：：detail ::completion_handler< boost::asio::detail::binder1< boost::reference_wrapper >，boost::system::error_code

boost::asio::detail::boost::asio::detail::task_io_service *，boost::asio::detail::boost::asio::detail::task_io_service_operation *，boost::system::error_code，‘boost/asio/detail/completion_handler.hpp:38:17:实例化自'boost::asio::detail ::completion_handler< boost::asio::detail::binder1< boost::reference_wrapper >，boost::system::error_code

::completion_handler( boost::asio::detail::binder1< boost::reference_wrapper >，boost::system::error_code )

)从'void：：asio：：boost/asio/detail/impl/task_io_service.hpp:50:3：::task_io_service::post( boost::asio::detail::binder1< boost::reference_wrapper >，boost::system::error_code‘实例化’

)‘boost/asio/impl/io_service.hpp:80:3:实例化自'void boost::asio::io_service::post(Handler)’boost/asio/basic_socket.hpp:649:9:实例化自'void boost::asio::basic_socket< boost::asio::ip::tcp，boost::asio::stream_socket_service ::async_connect( boost::asio::basic_socket >::boost ::asio::ip::basic_endpoint & )boost::reference_wrapper> )‘source.cpp:10:53:从这里实例化为boost/asio/detail/bind_handler.hpp:40:5:错误:不匹配对'( boost::reference_wrapper> ) (const boost::system::error_code &)’的调用。

Answer 1

看来你的签名是错的？您需要为error_code指定一个占位符

试一试

boost::signals2::signal<void(const boost::system::error_code&)> signal;
socket.async_connect(endpoint, boost::bind(boost::ref(signal), _1));

Answer 2

Ralf的answer很接近，我认为您需要将占位符绑定到signal函式：

#include <boost/signals2.hpp>
#include <boost/asio.hpp>

using namespace boost::asio;

int 
main() 
{
   io_service ios;
   ip::tcp::socket socket(ios);
   const ip::tcp::endpoint endpoint(
           ip::address::from_string(""), 
           0
           );

   boost::signals2::signal<void(const boost::system::error_code&)> signal;
   socket.async_connect(
           endpoint, 
           boost::bind(
               boost::ref(signal), _1
               ) 
       );
}

示例：

samm@macmini ~$ g++ -I /opt/local/include -L/opt/local/lib -Wl,-rpath,/opt/local/lib -lboost_system signal.cc 
samm@macmini ~$ echo $?
0
samm@macmini ~$