Headfirst设计模式的C++实现——迭代器(Iterator)改良版

iterator.h

 #ifndef _ITERATOR_H_
 #define _ITERATOR_H_

 class Iterator {
 public:
     virtual bool has_next() = ;
     virtual void *next() = ;
 };
 #endif

menu.h

 #ifndef _MENU_H_
 #define _MENU_H_

 class Menu {
 public:
     virtual Iterator *get_iterator() = ;
     virtual ~Menu() {};
 };
 #endif

diner_menu.h

 #ifndef _DINER_MENU_H_
 #define _DINER_MENU_H_

 #include "menu_item.h"
 #include "iterator.h"
 #include <vector>
 #include "menu.h"

 class DinerMenu : public Menu {
 public:
     void add_item(const std::string& name,
                   const std::string& description,
                   bool vegetarian,
                   double price) {
         menu_items.push_back( MenuItem(name, description, vegetarian, price) );
     }

     DinerMenu() : iterator( *this ) {
         add_item("diner name_1", "descrption_1", true, 4.5);
         add_item("diner name_2", "descrption_2", true, 6.2);
         add_item("diner name_3", "descrption_3", false, 3.5);
     }

     Iterator *get_iterator() {
         return &iterator;
     }
 private:
     class _Iterator : public Iterator {
     private:
         DinerMenu &menu;
         int pos;
     public:
         _Iterator( DinerMenu &_menu) : pos(), menu(_menu) {}
         bool has_next() { return pos < menu.menu_items.size(); }
         void* next() {
             return &(menu.menu_items[pos++]);
         }
     } iterator;

     std::vector<MenuItem> menu_items;
 };
 #endif

pancake_house_menu.h

 #ifndef _PANCAKE_HOUSE_MENU_H_
 #define _PANCAKE_HOUSE_MENU_H_

 #include "menu_item.h"
 #include "iterator.h"
 #include "menu.h"

 class PancakeHouseMenu : public Menu {
 public:
     void add_item(const std::string& name,
                   const std::string& description,
                   bool vegetarian,
                   double price) {
         if ( item_num < MAX_ITEMS ) {
            menu_items[item_num++] = new MenuItem( name, description, vegetarian, price );
         }
     }

     PancakeHouseMenu() : item_num(), iterator(*this) {
         add_item("name_1", "descrption_1", true, 4.5);
         add_item("name_2", "descrption_2", true, 6.2);
         add_item("name_3", "descrption_3", false, 3.5);
     }

     ~PancakeHouseMenu() {
         for ( int i = ; i < item_num; i++ ) {
             delete menu_items[i];
         }
     }

     Iterator *get_iterator() {
         return &iterator;
     }

 private:
     class _Iterator : public Iterator {
     private:
         PancakeHouseMenu &menu;
         int pos;
     public:
         _Iterator( PancakeHouseMenu &_menu) : pos(), menu(_menu) {}
         bool has_next() { return pos < menu.item_num; }
         void* next() {
             return menu.menu_items[pos++];
         }
     } iterator;

     const static int MAX_ITEMS = ;
     MenuItem *menu_items[MAX_ITEMS];
     int item_num;
 };
 #endif

main.cpp

 #include "pancake_house_menu.h"
 #include "diner_menu.h"
 #include <iostream>

 int main() {
     Menu * menus[] = { new PancakeHouseMenu, new DinerMenu };
     for ( int i = ; i < sizeof(menus)/sizeof(menus[]); i++ ) {
         Iterator *iterator = menus[i]->get_iterator();
         while ( iterator->has_next() ) {
             MenuItem *menu_item = (MenuItem *)iterator->next();
             std::cout << menu_item->get_name() << " "
                       << menu_item->get_description() << " "
                       << menu_item->is_vegetarian() << " "
                       << menu_item->get_price() << std::endl;
         }
         delete menus[i];
     }
 }