引用作为类成员的函数[关闭]

Question

所以我有这个意大利面条代码项目，我正在尝试使其面向对象。不幸的是，我遇到了我不太理解的错误，所以我尝试创建会引发相同错误而不会引发相同错误的简约代码。

---

下面是一些可以编译的简约代码：

（名为“ims.cpp”的文件）

#include <cstdio>

#include <ros/ros.h>

#include <visualization_msgs/Marker.h>
#include <visualization_msgs/InteractiveMarker.h>
#include <interactive_markers/interactive_marker_server.h>
#include <interactive_markers/menu_handler.h>

#include <rosbag/bag.h>
#include <rosbag/view.h>
#include <ros/param.h>

#include <fstream>
#include <cmath>
#include <boost/algorithm/string/split.hpp>
#include <boost/algorithm/string.hpp>

using namespace visualization_msgs;
using namespace geometry_msgs;
using namespace std;
using namespace boost;

boost::shared_ptr<interactive_markers::InteractiveMarkerServer> server;

void doNothing(const InteractiveMarkerFeedbackConstPtr &feedback){
}

void testServer(){

  InteractiveMarker inter_marker;
  inter_marker.header.frame_id = 1;
  Point pos;
  pos.x = 3;
  pos.y = 3;
  inter_marker.pose.position = pos;
  inter_marker.scale = 2;
  inter_marker.name = "testServer";

  server->insert(inter_marker, &doNothing);
}

int main(){}

解释：这是一个 ROS（机器人操作系统）项目，我仍然相信这是一个一般的 c++ 问题，所以我没有在他们的“ros::answers”论坛上问这个问题。请不要被类型混淆，我们会解决问题的。

函数“interactive_markers::InteractiveMarkerServer.insert”需要一个“visualization_msgs::InteractiveMarker &”和一个具有“InteractiveMarkerFeedbackConstPtr &”类型参数的函数，如提供的那样。 见：http://docs.ros.org/jade/api/interactive_markers /html/classinteractive__markers_1_1InteractiveMarkerServer.html

---

所以抛出我的错误的最小代码将是一个在“doNothing”函数中根本没有所需参数的代码，如下所示：

（名为“ims.cpp”的文件）

#include <as above>

using namespace visualization_msgs;
using namespace geometry_msgs;
using namespace std;
using namespace boost;

boost::shared_ptr<interactive_markers::InteractiveMarkerServer> server;

void doNothing(){
}

void testServer(){

  InteractiveMarker inter_marker;
  inter_marker.header.frame_id = 1;
  Point pos;
  pos.x = 3;
  pos.y = 3;
  inter_marker.pose.position = pos;
  inter_marker.scale = 2;
  inter_marker.name = "testServer";

  server->insert(inter_marker, &doNothing);
}

int main(){}

抛出错误：

    In file included from /usr/include/boost/function/detail/maybe_include.hpp:18:0,
                 from /usr/include/boost/function/detail/function_iterate.hpp:14,
                 from /usr/include/boost/preprocessor/iteration/detail/iter/forward1.hpp:52,
                 from /usr/include/boost/function.hpp:64,
                 from /opt/ros/indigo/include/ros/forwards.h:40,
                 from /opt/ros/indigo/include/ros/common.h:37,
                 from /opt/ros/indigo/include/ros/ros.h:43,
                 from /home/ros/ros/src/robotrainer_editor/heika_beta/ims/src/ims.cpp:3:
/usr/include/boost/function/function_template.hpp: In instantiation of ‘static void boost::detail::function::void_function_invoker1<FunctionPtr, R, T0>::invoke(boost::detail::function::function_buffer&, T0) [with FunctionPtr = void (*)(); R = void; T0 = const boost::shared_ptr<const visualization_msgs::InteractiveMarkerFeedback_<std::allocator<void> > >&]’:
/usr/include/boost/function/function_template.hpp:934:38:   required from ‘void boost::function1<R, T1>::assign_to(Functor) [with Functor = void (*)(); R = void; T0 = const boost::shared_ptr<const visualization_msgs::InteractiveMarkerFeedback_<std::allocator<void> > >&]’
/usr/include/boost/function/function_template.hpp:722:7:   required from ‘boost::function1<R, T1>::function1(Functor, typename boost::enable_if_c<boost::type_traits::ice_not<boost::is_integral<Functor>::value>::value, int>::type) [with Functor = void (*)(); R = void; T0 = const boost::shared_ptr<const visualization_msgs::InteractiveMarkerFeedback_<std::allocator<void> > >&; typename boost::enable_if_c<boost::type_traits::ice_not<boost::is_integral<Functor>::value>::value, int>::type = int]’
/usr/include/boost/function/function_template.hpp:1069:16:   required from ‘boost::function<R(T0)>::function(Functor, typename boost::enable_if_c<boost::type_traits::ice_not<boost::is_integral<Functor>::value>::value, int>::type) [with Functor = void (*)(); R = void; T0 = const boost::shared_ptr<const visualization_msgs::InteractiveMarkerFeedback_<std::allocator<void> > >&; typename boost::enable_if_c<boost::type_traits::ice_not<boost::is_integral<Functor>::value>::value, int>::type = int]’
/home/ros/ros/src/robotrainer_editor/heika_beta/ims/src/ims.cpp:40:42:   required from here
/usr/include/boost/function/function_template.hpp:112:11: error: too many arguments to function
           BOOST_FUNCTION_RETURN(f(BOOST_FUNCTION_ARGS));

这是有道理的，对吧？该函数没有所需的参数，因此编译器会抱怨。

---

所以现在我们解决了真正的问题：在面向对象的代码中，我遇到了同样的问题：

头文件

（名为“ims.h”的文件）

#include <cstdio>

#include <ros/ros.h>

#include <visualization_msgs/Marker.h>
#include <visualization_msgs/InteractiveMarker.h>
#include <interactive_markers/interactive_marker_server.h>
#include <interactive_markers/menu_handler.h>

#include <rosbag/bag.h>
#include <rosbag/view.h>
#include <ros/param.h>

#include <fstream>
#include <cmath>
#include <boost/algorithm/string/split.hpp>
#include <boost/algorithm/string.hpp>

using namespace visualization_msgs;
using namespace geometry_msgs;
using namespace std;
using namespace boost;

class IMS{

  boost::shared_ptr<interactive_markers::InteractiveMarkerServer> server;

  IMS();

  void doNothing(const InteractiveMarkerFeedbackConstPtr &feedback);

  void testServer();

  int main();

};

CPP 声明

（名为“ims.cpp”的文件）

#include <ims.h>

IMS::IMS(){}

void IMS::doNothing(const InteractiveMarkerFeedbackConstPtr &feedback){
}

void IMS::testServer(){

  InteractiveMarker inter_marker;
  inter_marker.header.frame_id = 1;
  Point pos;
  pos.x = 3;
  pos.y = 3;
  inter_marker.pose.position = pos;
  inter_marker.scale = 2;
  inter_marker.name = "testServer";

  server->insert(inter_marker, &IMS::doNothing); //other options that didn't work either: doNothing);//*this->doNothing(const InteractiveMarkerFeedbackConstPtr &feedback));//*this->doNothing());//this->doNothing);//&this->doNothing);//&IMS::doNothing);//&doNothing);
}

int IMS::main(){}

抛出错误：

In file included from /usr/include/boost/function/detail/maybe_include.hpp:18:0,
                 from /usr/include/boost/function/detail/function_iterate.hpp:14,
                 from /usr/include/boost/preprocessor/iteration/detail/iter/forward1.hpp:52,
                 from /usr/include/boost/function.hpp:64,
                 from /opt/ros/indigo/include/ros/forwards.h:40,
                 from /opt/ros/indigo/include/ros/common.h:37,
                 from /opt/ros/indigo/include/ros/ros.h:43,
                 from /home/ros/ros/src/robotrainer_editor/heika_beta/ims/include/ims.h:3,
                 from /home/ros/ros/src/robotrainer_editor/heika_beta/ims/src/ims.cpp:1:
/usr/include/boost/function/function_template.hpp: In instantiation of ‘static void boost::detail::function::function_void_mem_invoker1<MemberPtr, R, T0>::invoke(boost::detail::function::function_buffer&, T0) [with MemberPtr = void (IMS::*)(const boost::shared_ptr<const visualization_msgs::InteractiveMarkerFeedback_<std::allocator<void> > >&); R = void; T0 = const boost::shared_ptr<const visualization_msgs::InteractiveMarkerFeedback_<std::allocator<void> > >&]’:
/usr/include/boost/function/function_template.hpp:934:38:   required from ‘void boost::function1<R, T1>::assign_to(Functor) [with Functor = void (IMS::*)(const boost::shared_ptr<const visualization_msgs::InteractiveMarkerFeedback_<std::allocator<void> > >&); R = void; T0 = const boost::shared_ptr<const visualization_msgs::InteractiveMarkerFeedback_<std::allocator<void> > >&]’
/usr/include/boost/function/function_template.hpp:722:7:   required from ‘boost::function1<R, T1>::function1(Functor, typename boost::enable_if_c<boost::type_traits::ice_not<boost::is_integral<Functor>::value>::value, int>::type) [with Functor = void (IMS::*)(const boost::shared_ptr<const visualization_msgs::InteractiveMarkerFeedback_<std::allocator<void> > >&); R = void; T0 = const boost::shared_ptr<const visualization_msgs::InteractiveMarkerFeedback_<std::allocator<void> > >&; typename boost::enable_if_c<boost::type_traits::ice_not<boost::is_integral<Functor>::value>::value, int>::type = int]’
/usr/include/boost/function/function_template.hpp:1069:16:   required from ‘boost::function<R(T0)>::function(Functor, typename boost::enable_if_c<boost::type_traits::ice_not<boost::is_integral<Functor>::value>::value, int>::type) [with Functor = void (IMS::*)(const boost::shared_ptr<const visualization_msgs::InteractiveMarkerFeedback_<std::allocator<void> > >&); R = void; T0 = const boost::shared_ptr<const visualization_msgs::InteractiveMarkerFeedback_<std::allocator<void> > >&; typename boost::enable_if_c<boost::type_traits::ice_not<boost::is_integral<Functor>::value>::value, int>::type = int]’
/home/ros/ros/src/robotrainer_editor/heika_beta/ims/src/ims.cpp:19:47:   required from here
/usr/include/boost/function/function_template.hpp:225:11: error: no match for call to ‘(boost::_mfi::mf1<void, IMS, const boost::shared_ptr<const visualization_msgs::InteractiveMarkerFeedback_<std::allocator<void> > >&>) (const boost::shared_ptr<const visualization_msgs::InteractiveMarkerFeedback_<std::allocator<void> > >&)’
           BOOST_FUNCTION_RETURN(boost::mem_fn(*f)(BOOST_FUNCTION_ARGS));

---

诊断：

我的一个朋友实际上已经诊断出问题的合理来源：显然编译器将代码重新格式化为这个

void IMS::doNothing(IMS this, const InteractiveMarkerFeedbackConstPtr &feedback){

这当然会导致错误，因为参数不再符合我们的期望。

---

这是我的要求：

这个诊断正确吗？

如果是：是否可以解决？如何解决？

else：真正的问题是什么？

感谢所有阅读此长主题的人，并提前感谢您的回答！

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解决方案（根据“einpoklum”的建议）

最适合我的概念的解决方案是 lambda，它创建一个函数来包装恶意的“this”参数。

std::function 什么都没有 = [this] (const InteractiveMarkerFeedbackConstPtr &feedback) {this->doNothing(feedback);};

server->insert(inter_marker, nothing);

感谢您和所有费心阅读整个帖子的人，对于我难以理解地提出问题感到抱歉。

Answer 1

试图穿过大量文本并冒险回答：我认为（但不确定）问题是您试图将（非静态）成员函数传递为虽然它是一个独立的功能。

这应该行不通，因为你不能“像那样”调用成员函数——它必须有一个关联的对象。在实现层面上，需要使用类实例的地址来调用那段代码，以充当this 对象。

在这些情况下你可以做的是：

• 使用std::mem_fn 包装您的成员函数以获得正确的函数，其中额外的第一个参数是实例，或者
• 使用 lambda 以某种方式实例化对象（或仅将实例作为引用）并调用该实例的方法。 lambda 本身将退化为一个独立的函数，您可以传递其指针。
• 创建方法static - 如果它实际上不使用任何特定于实例的数据。