Pass unmanaged member function pointer to be used by wrapper to connect it to the signal in c++/cli

Question

I have implemented the Event Handling with Boost::Signal and Boost::Bind in my managed C++ file. Refered the Link:Boost::bind

Also I have created the function pointer in my native C++ file which is passed to my boost::Signal.Connect() as EventHandler in managed code. The code for function which is passed as function pointer in my Native C++

std::string NativeCplus::AddFunctionPointer( std::string message )  
{
return message;
}

and above function passed as boost::function object in another function NameChangeEvent() as below:

void NativeCplus::NameChangeEvent()
{
UnmanagedNameEvent* unmanagedNameEvent=new UnmanagedNameEvent();
boost::function<std::string (std::string)> f;
f=std::bind1st(std::mem_fun(&AlgebraAPI::AddFunctionPointer),this);//FunctionPointer

std::string name="abcd";
unmanagedNameEvent->AddEvent(f,name);
}

In the above code ,I have taken the boost::function and the function pointer is converted to that boost::function (f).(AM I RIGHT IN SAYING THIS?).Then the line unmanagedNameEvent->AddEvent(f,name) where boost::function(f) is passed to AddEvent(f,name) and this AddEvent(f,name) is implemented in my managed C++ code file. Below is my managed C++ Code which is being referred in the native c++ project:

//In my c++/CLI Wrapper.cpp

    declspec(dllexport) void UnmanagedNameEvent::AddEvent(boost::function<std::string (std::string)> f,std::string name)
        {

                UnmanagedNameEvent* unmanagedNameEvent=new UnmanagedNameEvent();
            unmanagedNameEvent->signalEventMessage.connect(f);
//which should be like this.. unmanagedNameEvent->signalEventMessage.connect(bind(NativeCplus::f));

        }

PROBLEM is I can't use the NativeCplus class to refer to its unmanaged function (i.e.f)as that will create a round dependency of dll file.Any workaround for this?All ears for any shorter solution!!

Answer 1

Here is a sample of what I understand you want:

Your C++/CLI "wrapper":

Market.h:

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

class __declspec(dllexport) Market
{
    private: boost::signals2::signal<void(double)> signalEvent;
    public: void AddHandler(boost::function<void(double)> handler);
    public: void Move(double value);
};

Market.cpp:

#include "Market.h"

#include <boost/function.hpp>

void Market::AddHandler(boost::function<void(double)> handler)
{
    signalEvent.connect(handler);
}

void Market::Move(double value)
{
    signalEvent(value);
}

And your native app, test.cpp:

#include <iostream>

#include <boost/function.hpp>
#include <boost/bind.hpp>

#include "Market.h"

class Investor
{
    public: void move_handler(double value)
    {
        std::cout << (value >= 0 ? "Hey! I'm the best!" : "Wat! I'm losing my shirt! ") << std::endl;
    }
};

int main()
{
    Investor investor;

    Market market;

    boost::function<void(double)> move = boost::bind(&Investor::move_handler, &investor, _1);

    market.AddHandler(move);

    market.Move(+0.10);
    market.Move(-0.10);
}

Results:

Hey! I'm the best!
Wat! I'm losing my shirt!

Hope this helps...