Refer to a function that is member of a class [closed] - c++

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So i have this spaghetti-code project which i'm trying to make object oriented. Pittily i have encountered errors that i didn't quite understand, so i tried creating minimalistic code that does throw the same errors and that doesn't.
So here is some minimalistic code that compiles:
(File named "ims.cpp")
#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(){}
Explenation: this is a ROS (robot operating system) project, still i believe this is a general c++ issue so i didn't ask the question in their "ros::answers" forum. Please don't get confused by types, we'll get to the problem.
The function "interactive_markers::InteractiveMarkerServer.insert" requires a "visualization_msgs::InteractiveMarker &" and a function that has a parameter of type "InteractiveMarkerFeedbackConstPtr &", as provided.
see: http://docs.ros.org/jade/api/interactive_markers
/html/classinteractive__markers_1_1InteractiveMarkerServer.html
So a minimal code throwing my error would be one that simply doesn't have the required parameter in the "doNothing" function, like this:
(File named "ims.cpp")
#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(){}
throwing the error:
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));
Which makes sense, right? The function doesn't have the parameter required, so the compiler complains.
So NOW we get to the true issue: in an object oriented code, i have the same problem:
HEADER FILE
(File named "ims.h")
#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 DECLARATION
(File named "ims.cpp")
#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(){}
throwing the error:
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));
Diagnosis:
a friend of mine actually allready diagnosed a plausible source of the problem: apperently the compiler reformats the code to this
void IMS::doNothing(IMS this, const InteractiveMarkerFeedbackConstPtr &feedback){
which of course leads to the error, as the parameter doesn't fit our expectations anymore.
So here is my request:
Is this diagnosis correct?
if yes: can it be workarounded and how?
else: what is the actual problem?
Thanks anyone who even reads this long thread entirely, and thank you in advance for your answers!
Solution (following a suggestion by "einpoklum")
The solution the most fitting for my concept was a lambda, creating a functiuon to wrap the malicious "this" parameter.
std::function nothing =
[this] (const InteractiveMarkerFeedbackConstPtr &feedback) {this->doNothing(feedback);};
server->insert(inter_marker, nothing);
Thank you and everyone who bothered reading the whole thread very much, sorry for my difficulties asking the question understandably.

Answer 1

Trying to cut through the mountains of text and venture an answer: I think (but am not certain) the problem is you trying to pass a (non-static) member function as though it were a free-standing function.
That should not work, since you can't call a member function "just like that" - it has to have an associated object. On the implementation level, that piece of code needs to be called with the address of an instance of the class to serve as the this object.
What you can do in these situations is:
Wrap your member functions using std::mem_fn to get a proper function, with an extra first argument being the instance, or
Use a lambda which instantiates an object somehow (or just takes an instance as a reference) and invokes that instance's method. The lambda itself will degenerate into a freestanding function whose pointer you can pass around.
Make the method static - if it doesn't actually use any instance-specific data.