shapefactory1.cpp

C++编程思想第二版第一册答案

//: C25:ShapeFactory1.cpp
// From Thinking in C++, 2nd Edition
// Available at http://www.BruceEckel.com
// (c) Bruce Eckel 1999
// Copyright notice in Copyright.txt
#include "../purge.h"
#include <iostream>
#include <string>
#include <exception>
#include <vector>
using namespace std;

class Shape {
public:
  virtual void draw() = 0;
  virtual void erase() = 0;
  virtual ~Shape() {}
  class BadShapeCreation : public exception {
    string reason;
  public:
    BadShapeCreation(string type) {
      reason = "Cannot create type " + type;
    }
    const char *what() const { 
      return reason.c_str(); 
    }
  };
  static Shape* factory(string type) 
    throw(BadShapeCreation);
};

class Circle : public Shape {
  Circle() {} // Private constructor
  friend class Shape;
public:
  void draw() { cout << "Circle::draw\n"; }
  void erase() { cout << "Circle::erase\n"; }
  ~Circle() { cout << "Circle::~Circle\n"; }
};

class Square : public Shape {
  Square() {}
  friend class Shape;
public:
  void draw() { cout << "Square::draw\n"; }
  void erase() { cout << "Square::erase\n"; }
  ~Square() { cout << "Square::~Square\n"; }
};

Shape* Shape::factory(string type) 
  throw(Shape::BadShapeCreation) {
  if(type == "Circle") return new Circle();
  if(type == "Square") return new Square();
  throw BadShapeCreation(type);
}

char* shlist[] = { "Circle", "Square", "Square",
  "Circle", "Circle", "Circle", "Square", "" };

int main() {
  vector<Shape*> shapes;
  try {
    for(char** cp = shlist; **cp; cp++)
      shapes.push_back(Shape::factory(*cp));
  } catch(Shape::BadShapeCreation e) {
    cout << e.what() << endl;
    return 1;
  }
  for(int i = 0; i < shapes.size(); i++) {
    shapes[i]->draw();
    shapes[i]->erase();
  }
  purge(shapes);
} ///:~