C++ delegate template

Question

If I have the following setup, just example. The problem I have is to get the connect function of the template to work.

class A
{
public:
   Delegate<void(int)> test;
};


class B
{
public:
    void test(int a)
    {
       std::cout << a;
    };

};

I want to connect this with the following: a.test.connect(&b, &B::test);

Then an instance of class a can call the test function on an instance of class B.

I have the following template, but have problem to capture the instance and function I need.

#ifndef DELEGATE_H
#define DELEGATE_H

#include <functional>

template<class _Delegate>
class Delegate;


template<class R, class... Args>
class Delegate<R(Args...)>
{
public:
    template<typename T>
    void connect(T* t, R(Args... ) ) 
    {
        mFunction = std::function(T::*t, R(Args...));; 

    }

    R operator()(Args... args)
    {
        return mFunction(args...);
    }

protected:
    std::function<R(Args...)> mFunction;
};

#endif

Answer 1

Your connect() should be written almost as follows

  template<typename T>
  void connect (T * t, R(T::*method)(Args...) ) 
   { mFunction = [=](Args ... as){ (t->*method)(as...); }; }

The following is a full compiling example

#include <iostream>
#include <functional>

template <typename>
class Delegate;

template <typename R, typename... Args>
class Delegate<R(Args...)>
 {
   public:
      template<typename T>
      void connect (T * t, R(T::*method)(Args...) ) 
       { mFunction = [=](Args ... as){ (t->*method)(as...); }; }

      R operator() (Args... args)
       { return mFunction(args...); }

   protected:
      std::function<R(Args...)> mFunction;
 };

class A
 { public: Delegate<void(int)> test; };

class B
 { public: void test (int a) { std::cout << a; }; };

int main()
 {
   A a;
   B b;

   a.test.connect(&b, &B::test);

   a.test(42);
 }