How to call virtual function for all created objects which are inherited from the one? C++

Question

For example, I have three classes: A, B::A and C::A, only B and C have virtual method print(), like that:

#include <iostream>

using namespace std;

class A {
public:
    virtual void print() {
        return;
        //do nothing
    }

    static void Func() {
        //how to call all virtual functions print() for one class A?
        print(); //doesn't work
    }
};

class B : public A {
public:
    virtual void print() {
        cout << "B" << endl;
    }
};

class C : public A {
public:
    virtual void print() {
        cout << "C" << endl;
    }
};

int main() {
  B b1;
  B b2
  C c;
  A::Func();
  return 0;
}

I wan't use print() for all inherited objects (b1, b2, c) by using just class A. How can I do it?

Answer 1

Declare a static class member of A that's a container of pointers to all instances of A or its subclasses. A std::list will be an excellent choice:

class A {
   static std::list<A *> all_instances;
public:

   // ...
};

In A's constructor, add its this to the list, saving the new list entry's iterator. In A's destructor, remove its list entry from the list.

So now you will have a private container that enumerates all instances of A , or any of its subclasses.

Writing a static class method that invokes each one's print() method becomes trivial, at this point.

Of course, a little bit of additional work is necessary to implement thread safety, if it's an issue here.

Writing the code for A's constructor or destructor will be your homework assignment.