Example for a templated class data member that is "virtual". The virtual function that wraps around the data member, gets it to behave as a virtual data member.

"Virtual" Data Members

#include <iostream>

using namespace::std;

template<typename A>
class base {

  protected:
    A data;

  public:
    virtual void set_value (A value) { data = value; }
    virtual A return_data() = 0;
    virtual void print() = 0;
};

template<typename A>
class derived : public base<A> {

  float a;
  public:
    void set_value(A value) { this->data = value; }
    A return_data() { return this->data;}
    void print() { cout << "Print derived a value " << a << endl; }
};

int main() {

  base<int> *obj = new derived<int>();

  obj->set_value(10);
  int b = obj->return_data();
  cout << "b value " << b << endl;

  obj->print();

  return 0;
}