How to pass an implemented virtual member function as a parameter - c++

Question

#include <iostream>
class virtualClass{
public:
virtual int a() = 0;
};
class UnknownImplementation : public virtualClass{
public:
int a() override { return 1;}
};
class myFramework {
public:
int c(int (virtualClass::*implementedFunc)(void)){
implementedFunc();
return 2;
}
};
int main(){
//some user implements the virtual class and calls myFramework function
myFramework* mfp = new myFramework();
std::cout << mfp->c(&(UnknownImplementation::a)) << std::endl;
}
Hi, I am working on a framework that is supposed call an implemented virtual function and use it. It is similar to the code above.
The compiling errors I get are:
testVirtual.cpp: In member function ‘int myFramework::c(int (virtualClass::)())’: testVirtual.cpp:16:19: error: must use ‘.’ or
‘->’ to call pointer-to-member function in ‘implementedFunc (...)’,
e.g. ‘(... -> implementedFunc) (...)’ implementedFunc();
^ testVirtual.cpp: In function ‘int main()’: testVirtual.cpp:24:47: error: invalid use of non-static member
function ‘virtual int UnknownImplementation::a()’ std::cout <<
mfp->c(&(UnknownImplementation::a)) << std::endl;
How do I fix these problems?
Thanks in advance!
passing an instance of the implemented class and calling the function worked.

Answer 1

To build on sameerkn's comment, this code should be:
#include <iostream>
class virtualClass{
public:
virtual int a() = 0;
};
class mySubclass : public virtualClass{
public:
int a() override { return 1;}
};
int main(){
mySubclass * x= new mySubclass ();
// ...
std::cout << x->a () << std::endl;
}
The point here is that you can pass objects (or pointers) of type virtualClass around - even though they might actually be mySubclass objects in real life - and still wind up in the right implementation of a(). myFramework is entirely unnecessary.
That's what virtual methods are for - consumers of virtualClass don't need to know anything about classes that might - now or in the future - be derived from it, and if I have read your question correctly, this is what you want.