Headfirst设计模式的C++实现——简单工厂模式(Simple Factory)之二

为了引出后续的工厂方法，把在简单工厂模式的基础上增加了新功能——加盟店

简而言之就是把原来的单一简单工厂（能生产cheese和greek两种pizza）细分成了纽约地区的和芝加哥地区的（每种地区都能生产cheese和greek两种pizza）

和之前的简单工厂相比，PizzaStore中的PizzaFactory由构造时传入一个引用，从SimplePizzaFactory中派生出两个类，原来的cheese和greek Pizza也根据地区做了扩展。

Pizza.h

 #ifndef _PIZZA_H
 #define _PIZZA_H
 #include <iostream>
 #include <string>

 class Pizza
 {
 public:
     Pizza(const std::string &type) : m_type(type) {}
     virtual ~Pizza() {}
     virtual void prepare() { std::cout << "prepare " << m_type << std::endl; }
     virtual void bake() { std::cout << "bake " << m_type << std::endl; }
     virtual void cut() { std::cout << "cut " << m_type << std::endl; }
     virtual void box() { std::cout << "box " << m_type << std::endl; }
 private:
     std::string m_type;
 };
 #endif

ChiChagoCheesePizza.h

 #ifndef _CHICHAGO_CHEESE_PIZZA_H
 #define _CHICHAGO_CHEESE_PIZZA_H
 #include <iostream>
 #include "Pizza.h"

 class ChiChagoCheesePizza : public Pizza
 {
 public:
     CChiChagoheesePizza() : Pizza("chichago cheese") {}
     ~ChiChagoCheesePizza() {}
 };
 #endif

ChiChagoGreekPizza.h

 #ifndef _CHICHAGO_GREEK_PIZZA_H
 #define _CHICHAGO_GREEK_PIZZA_H
 #include <iostream>
 #include "Pizza.h"

 class ChiChagoGreekPizza : public Pizza
 {
 public:
     ChiChagoGreekPizza() : Pizza("chichago greek") {}
     ~ChiChagoGreekPizza() {}
 };

 #endif

NYCheesePizza.h

 #ifndef _NY_CHEESE_PIZZA_H
 #define _NY_CHEESE_PIZZA_H
 #include <iostream>
 #include "Pizza.h"

 class NYCheesePizza : public Pizza
 {
 public:
     NYCheesePizza() : Pizza("ny cheese") {}
     ~NYCheesePizza() {}
 };
 #endif

NYGreekPizza.h

 #ifndef _NY_GREEK_PIZZA_H
 #define _NY_GREEK_PIZZA_H
 #include <iostream>
 #include "Pizza.h"

 class NYGreekPizza : public Pizza
 {
 public:
     NYGreekPizza() : Pizza("ny greek") {}
     ~NYGreekPizza() {}
 };

 #endif

SimplePizzaFactory.h

 #ifndef _SIMPLE_PIZZA_FACTORY
 #define _SIMPLE_PIZZA_FACTORY

 #include "Pizza.h"

 class SimplePizzaFactory
 {
 public:
     virtual Pizza *CreatePizza(const std::string &type) = ;
 };
 #endif

ChiChagoPizzaFactory.h

 #ifndef _CHICHAGO_PIZZA_FACTORY_H
 #define _CHICHAGO_PIZZA_FACTORY_H

 #include "SimplePizzaFactory.h"
 #include "ChiChagoCheesePizza.h"
 #include "ChiChagoGreekPizza.h"

 class ChiChagoPizzaFactory : public SimplePizzaFactory
 {
 public:
     Pizza *CreatePizza(const std::string &type)
     {
         if ( "cheese" == type )
         {
             return new ChiChagoCheesePizza();
         }
         if ( "greek" == type )
         {
             return new ChiChagoGreekPizza();
         }
         return NULL;
     }
 };
 #endif

NYPizzaFactory.h

 #ifndef _NY_PIZZA_FACTORY_H
 #define _NY_PIZZA_FACTORY_H

 #include "SimplePizzaFactory.h"
 #include "NYCheesePizza.h"
 #include "NYGreekPizza.h"

 class NYPizzaFactory : public SimplePizzaFactory
 {
 public:
     Pizza *CreatePizza(const std::string &type)
     {
         if ( "cheese" == type )
         {
             return new NYCheesePizza();
         }
         if ( "greek" == type )
         {
             return new NYGreekPizza();
         }
         return NULL;
     }
 };
 #endif

PizzaStore.h

 #ifndef _PIZZA_STORE_H
 #define _PIZZA_STORE_H
 #include "SimplePizzaFactory.h"

 class PizzaStore
 {
 private:
     SimplePizzaFactory &m_pizza_factory;
 public:
     PizzaStore(SimplePizzaFactory &pizza_factory) : m_pizza_factory(pizza_factory) {}
     Pizza* OrderPizza(const std::string &type)
     {
         Pizza *p_pizza = m_pizza_factory.CreatePizza(type);
         if (p_pizza)
         {
             p_pizza->prepare();
             p_pizza->bake();
             p_pizza->cut();
             p_pizza->box();
         }
         return p_pizza;
     }
 };
 #endif

main.cpp

 #include "PizzaStore.h"
 #include "NYPizzaFactory.h"
 int main()
 {
     NYPizzaFactory ny_pizza_factory;
     PizzaStore pizza_store(ny_pizza_factory);
     Pizza *p_pizza = pizza_store.OrderPizza("greek");
     if ( p_pizza )
     {
         delete p_pizza;
     }
     return ;
 }