CODEWITHSUNDEEP
c++pointer-to-member
Fl0wless
Fl0wless

Reputation: 358

function pointer to any member function with any number of arguments

because of specific reasons I want a function pointer that can point to any member function of the class and can be changed whenever I want. I thought of a setup like the following:

//#include <iostream>
//#include <functional>
#include <cstdarg>

class someclass{
public:
    someclass(){ func = trial; }
    template<typename T, typename... Args> void setfunc(T t, Args... args){
        func = t(args...);
    }
    void trial(){
        //do some stuff
    }
    void trying(int i){
        //do other stuff
    }
    template <typename T>void (someclass::*func)(Args...);

};

int main(){
    someclass c;
    (c.*(c.func))();
    c.setfunc(someclass::trying, 32);
    (c.*(c.func))();

}

Unfortunately C++ doesn't let me do that and instead gives me the error:

data member 'func' cannot be a member template

I read that you can't make templates of member variables and when I write

void (someclass::*func)();

and scram the Args-part in setfunc(), it works just fine for trial(), but not for trying(). So my question is: is there anyway to fix this, work around it or any other way I can try?

Temporarily I'm here:

#include <iostream>
#include <functional>
class someclass{
public:
   someclass(){
        func = std::bind(&someclass::trial, std::placeholders::_1);
    }
    void setfunc(std::function<void(someclass&)> f){ func = f; }
    void trial(){
        //do some stuff
        //std::cout << "1" << std::endl;
    }
    void trying(int i){
        //do other stuff
        //std::cout << "2" << std::endl;
    }
    std::function<void(someclass&)> func;
};

int main(){
    someclass c;
    #c.func(); //!!!
    c.setfunc(std::bind(&someclass::trying, std::placeholders::_1, 32));
    #c.func(c); //!!!
}

My IDE marks the lines with the #

Upvotes: 0

Views: 119

Answers (1)

Jarod42
Jarod42

Reputation: 218343

You may use std::function, something like

class someclass{
public:
    someclass(){ func = &someclass::trial; }
    void setfunc(std::function<void(someclass&)> f){ func = f; }
    void trial(){
        //do some stuff
    }
    void trying(int i){
        //do other stuff
    }
    std::function<void(someclass&)> func;
};

int main(){
    someclass c;
    c.func(c);
    c.setfunc([](someclass& cl){cl.trying(32);});
    c.func(c);
}

Upvotes: 1

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