#include <iostream>
#include <vector>
using namespace std;


class A
{
      protected:
             virtual int Add() { cout << "Hello"; }

      public:
             void Dec() { cout << "\n"; }

      private:
              int a;
};


class B : public A
{
      public:
             virtual int Add(int a) { A::Add(); cout << " World"; }
};

class C : public A
{
      public:
             virtual int Add() { cout << "!"; }
};


// ==================================================
class Factory
{
      public:
             Factory() {}

      public:
             A* CreateObject(int a)
             {
                    if (a == 0)
                       return new B();
                    else if (a == 1)
                       return new C();
             }
};
// ==================================================


int main(void)
{
    Factory f;
    B *b = dynamic_cast<B*>(f.CreateObject(0));
    C *c = dynamic_cast<C*>(f.CreateObject(1));

    b->Add(5);
    c->Add();
    b->Dec();
    c->Dec();
    c->Add();

    delete c;
    delete b;

    // --------------------------------------
    cout << endl << "=====================================" << endl << endl;

    B* arrB[3];
    arrB[0] = dynamic_cast<B*>(f.CreateObject(0));
    arrB[1] = dynamic_cast<B*>(f.CreateObject(1)); // <----| ???
    arrB[2] = dynamic_cast<B*>(f.CreateObject(0));

    //arrB[1]->Add(4); // error?

    delete arrB[0];
    delete arrB[1];
    delete arrB[2];

    return 0;
}