#include <iostream>
#include <vector>

using namespace std;

class Base {
   public:
      virtual ~Base()=default;
      virtual void Print() {
         cout << "a = " << a  << endl;
      }
   private:
      int a = 7;
};

class Derived1: public Base {
   public:
      Derived1():id(++count){};
      virtual void Print() {
         Base::Print();
         cout << "b = " << b << endl;
      }

      int ID(void) const {
          return id;
      }

      vector<int> & Data(void) {
          return data;
      }

   private:
      int b = 9;
      static inline int count = 0;
      vector <int> data{99, 99, 99, 99};
      const int id;
};


void PrintMe( Derived1 * derivedPtr){

   if (derivedPtr == nullptr) {
      cout << "Nope, it is a null pointer!" << endl;
   } else {
        derivedPtr->Print();
        {
            cout << "My ID is " << derivedPtr->ID() << endl; 
            vector<int> & d = derivedPtr->Data();
            for(auto x: d) {
               cout << x << " " ;
            }
        }
        cout << endl;
   }
}

int main() {

    Base a;
    Derived1 b;

    Base * basePtr = nullptr;
    Derived1 * derivedPtr = nullptr;

    cout << "The base class is " << endl;
    a.Print();
    cout << endl;

    cout << "The derived class is " << endl;
    b.Print();
    cout << endl;


    // allowed and should work fine.
    cout << "basePtr at Derived print call " << endl;
    basePtr = new Derived1;
    basePtr->Print();
    cout << endl;

    cout << "derivedPtr at Derived print after cast from base call " << endl;
    //derivedPtr = basePtr;
    derivedPtr = static_cast<Derived1 *>(basePtr);
    PrintMe(derivedPtr);

    delete derivedPtr;

    basePtr = new Base;
    cout << "basePtr at base print call " << endl;
    basePtr->Print();
    cout << endl;


    // this is bad.
    cout << "derivedPtr at base print after cast from base call " << endl;
    derivedPtr = static_cast<Derived1 *>(basePtr);
    //PrintMe(derivedPtr);

    // this is safe
    derivedPtr = dynamic_cast<Derived1 *>(basePtr);
    PrintMe(derivedPtr);

    return 0;
}