shapev2.cpp

Thinking in C++ 2nd edition source code which are all the cores of the book Thinking in C++ second e

//: C:ShapeV2.cpp
// From Thinking in C++, 2nd Edition
// at http://www.BruceEckel.com
// (c) Bruce Eckel 1999
// Copyright notice in Copyright.txt
// Alternative to ShapeV.cpp
#include <iostream>
#include <vector>
#include "../purge.h"
using namespace std;

class Shape {
  Shape(Shape&); // No copy-construction
protected:
  Shape() {} // Prevent stack objects
  // But allow access to derived constructors
public:
  enum type { tCircle, tSquare, tTriangle };
  virtual void draw() = 0;
  virtual ~Shape() { cout << "~Shape\n"; }
  static Shape* make(type);
};

class Circle : public Shape {
  Circle(Circle&); // No copy-construction
  Circle operator=(Circle&); // No operator=
protected:
  Circle() {};
public:
  void draw() { cout << "Circle::draw\n"; }
  ~Circle() { cout << "~Circle\n"; }
  friend Shape* Shape::make(type t);
};

class Square : public Shape {
  Square(Square&); // No copy-construction
  Square operator=(Square&); // No operator=
protected:
  Square() {};
public:
  void draw() { cout << "Square::draw\n"; }
  ~Square() { cout << "~Square\n"; }
  friend Shape* Shape::make(type t);
};

class Triangle : public Shape {
  Triangle(Triangle&); // No copy-construction
  Triangle operator=(Triangle&); // Prevent
protected:
  Triangle() {};
public:
  void draw() { cout << "Triangle::draw\n"; }
  ~Triangle() { cout << "~Triangle\n"; }
  friend Shape* Shape::make(type t);
};

Shape* Shape::make(type t) {
  Shape* S;
  switch(t) {
    case tCircle: S = new Circle; break;
    case tSquare: S = new Square; break;
    case tTriangle: S = new Triangle; break;
  }
  S->draw(); // Virtual function call
  return S;
}

int main() {
  vector<Shape*> shapes;
  cout << "virtual constructor calls:" << endl;
  shapes.push_back(Shape::make(Shape::tCircle));
  shapes.push_back(Shape::make(Shape::tSquare));
  shapes.push_back(Shape::make(Shape::tTriangle));
  cout << "virtual function calls:\n";
  for(int i = 0; i < shapes.size(); i++)
    shapes[i]->draw();
  //!Circle c; // Error: can't create on stack
  purge(shapes);
} ///:~