Calling derived function in base class

[eviltwinkie]

Hello, currently I am trying to do this:

class A {
	doFunction(void(*f)()){ f(); }	
}

class B : public A {
	int b;
	void func() { b = 1; cout << b << endl; }
	doFunc() { doFuntion(&func); }
}

I see the obvious problems with this. doFunction requires void(*)() and doFunc is passing void(B::*)(). I know it seems odd that I would want to do this, but it's just a very small part of what I am trying to accomplish. I need to have the base class A be able to call a function from derived class B, and this function cannot be virtual.
Any help is appreciated.

[Bazzy]

In A::doFunction you are calling f without any reference to a B object, to which object should that function be applied?
Can you be a bit more specific about what you actually need?

[eviltwinkie]

Is there a way I can reference a B object even though B is derived from A?
Specifically, B::func() is a function that modifies B's members. I need A::doFunction to call func() in a way it still modifies B's members.

[Bazzy]

You can use B objects in A methods:

class B;
struct A {
	void doFunction(void(B::*f)());
};

struct B : public A {
	int b;
	void func() { b = 1; cout << b << endl; }
	void doFunc() { doFunction(&B::func); }
};


void A::doFunction(void(B::*f)())
{
    B someobject;
    (someobject.*f)();
}	

But still, where would someobject come from?

[eviltwinkie]

Is there I can do this with A not knowing at all about B by using templates? I am not well versed in polymorphism. The end result of what doFunction will be used for is something like this:

class A {
	void doFunction(void(*f)()) { f(); }	
};

class B : public A {
	int b;
	void func() { b = 1; cout << b << endl; }
	void doFunc() { doFuntion(&func); }
};

class C : public A {
	int c;
	void func() { c = 1; cout << c << endl; }
	void doFunc() { doFuntion(&func); }
};

[guestgulkan]

There is this pattern used for what is called static polymorphism

Example1

template <typename T>
class base
{

protected:

    void DoFunction()
    {
        ((T*)this)->func();
    }


};

class Derived : public base<Derived>
{
public:

    int a;
    
    void func()
    {
        a = 4;

    }
    
    void DoFunc()
    {
        DoFunction();

    }
};



int main(int argc, char *argv[]) 
{
    
    Derived d;
    d.DoFunc();
}
    

Example2

template <typename T>
class base
{

protected:

    void DoFunction( void(T::* f)() )
    {
        (((T*)this)->*f)();
    }


};

class Derived : public base<Derived>
{
public:

    
    void func()
    {
        cout << "Derived::func" << endl;

    }

    void func2()
    {
        
        cout << "Derived::func2" << endl;
    }
    
    void DoFunc()
    {
        
        DoFunction(&Derived::func);
        DoFunction(&Derived::func2);

    }
};



int main(int argc, char *argv[]) 
{
    
    Derived d;
    d.DoFunc();
}
    

[eviltwinkie]

Thank you both for you help so far. guestgulkan, I think that is a bit closer to what I need. Would something like this work?

template <typename T>
class A {
	void doFunction(void(T::*f)()){ 
		((T*)this)->f(); 
	}	
}

class B : public A<B> {
	int b;
	void func() { b = 1; cout << b << endl; }
	void doFunc() { doFuntion(&func); }
}

[guestgulkan]

I edited my code to show a function pointer example

[eviltwinkie]

Thank you!