Headfirst设计模式的C++实现——迭代器(Iterator)

iterator.h

 #ifndef _ITERATOR_H_
 #define _ITERATOR_H_

 #include "menu_item.h"

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

menu_item.h

 #ifndef _MENU_ITEM_H_
 #define _MENU_ITEM_H_

 #include <string>

 class MenuItem {
 private:
     std::string name;
     std::string description;
     bool vegetarian;
     double price;
 public:
     MenuItem( const std::string &_name,
               const std::string _description,
               bool _vegetarian,
               double _price) :
         name(_name),
         description(_description),
         vegetarian(_vegetarian),
         price(_price) {}

     std::string get_name() { return name; }
     std::string get_description() { return description; }
     double get_price() { return price; }
     bool is_vegetarian() { return vegetarian; }
 };
 #endif

pancake_house_menu.h

 #ifndef _PANCAKE_HOUSE_MENU_H_
 #define _PANCAKE_HOUSE_MENU_H_

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

 class PancakeHouseMenu {
 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; }
         MenuItem *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 <iostream>

 int main() {
     PancakeHouseMenu menu;
     Iterator *iterator = menu.get_iterator();
     while ( iterator->has_next() ) {
         MenuItem *menu_item = iterator->next();
         std::cout << menu_item->get_name() << " "
                   << menu_item->get_description() << " "
                   << menu_item->is_vegetarian() << " "
                   << menu_item->get_price() << std::endl;
     }
 }