#include <iostream>
#include <vector>
#include <cstdlib>

using namespace std;

class Shape {
public:
  Shape() {};
  void setColor() {
    cout << " Shape::setColor() called "<< endl;
  }
  virtual void Draw() =0;  // declare as pure virtual
  //..
};
class Rectangle : public Shape {
public:
  int ncorners;
  Rectangle () { ncorners = 4;};
  void Draw() {
    cout << " Rectangle::Draw() called "<< endl;
  }
  void ShowCorners() {
    cout << " Rectangle::ShowCorners() called "<< ncorners << endl;
  }

};
class Oval  : public Shape {
public:
     void Draw() {
       cout << " Oval::Draw() called "<< endl;
     }
};
class RoundRect : public Shape {
public:
     void Draw() {
       cout << " RoundRect::Draw() called "<< endl;
     }
};

void gimeSomeShapes( vector<Shape*> &vs, int nshapes )
{
    // create concrete shapes randomly and add to vector
  for ( int i=0; i<nshapes; i++) {
    int irand = static_cast<int>(rand()*3./(RAND_MAX+1.0)); // Zufallszahlen [0..3)
    switch (irand ) {
    case 0:
      vs.push_back( new Rectangle());
      break;
    case 1:
      vs.push_back( new Oval());
      break;
    case 2:
      vs.push_back( new RoundRect());
      break;
    }
  }
}
int main ()
{
  vector<Shape*> vecshape;  // vector with base-class pointers
  gimeSomeShapes( vecshape, 10 ); // erzeuge shapes

  for ( int i=0; i<vecshape.size(); i++ ){
    vecshape[i]->setColor( ); 
    vecshape[i]->Draw( );     
    vecshape[i]->ShowCorners( );     // won't work
  }
}