迭代器模式就是常见的集合中的Itrerator。
迭代器模式定义：提供一种方法顺序访问一个集合对象中的各个元素，有不暴露其内部是如何表示的。
可以用来处理集合之间不同类型数据的管理
代码如下
//定义迭代器
public interface Iterator
{
object Next();
bool HasNext();
}
//定义菜单接口
public interface Menu
{
Iterator CreateIterator();
}
//定义菜单属性类
public class MenuItem
{
string name;
string description;
bool isVegetarian;
double price;
public string Name
{
get { return name; }
set { name = value; }
}
public string Description
{
get { return description; }
set { description = value; }
}
public bool IsVegetarian
{
get { return isVegetarian; }
set { isVegetarian = value; }
}
public double Price
{
get { return price; }
set { price = value; }
}
public MenuItem(string name,
string description,
bool isVegetarian,
double price)
{
this.name = name;
this.description = description;
this.isVegetarian = isVegetarian;
this.price = price;
}
}
//定义晚餐哈希表迭代器
public class CafeMenuIterator : Iterator
{
Hashtable menuItems = new Hashtable();
int position = 1;
public CafeMenuIterator(Hashtable menuItems)
{
this.menuItems = menuItems;
}
public bool HasNext()
{
return menuItems.Count < position ? false : true;
}
public object Next()
{
MenuItem menu = (MenuItem)menuItems[position];
position += 1;
return menu;
}
}
//定义晚餐类
public class CafeMenu : Menu
{
Hashtable menuItems = new Hashtable();
public CafeMenu()
{
AddItem("Veggie Burger and Air Fries",
"Veggie burger on a whole wheat bun, lettuce, tomato, and fries",
true, 3.99, 1);
AddItem("Soup of the Day",
"A cup of the soup of the day, with a side salad",
false, 3.69, 2);
AddItem("Burrito",
"A large burrito, with whole pinto beans, salsa, guacamole",
true, 4.29, 3);
}
public void AddItem(string name, string description,
bool isVegetarian, double price, int index)
{
MenuItem menuItem = new MenuItem(name, description, isVegetarian, price);
menuItems.Add(index, menuItem);
}
public Iterator CreateIterator()
{
return new CafeMenuIterator(menuItems);
}
}
//定义午餐数组迭代器
public class DinnerMenuIterator : Iterator
{
MenuItem[] items;
int position = 0;
public DinnerMenuIterator(MenuItem[] items)
{
this.items = items;
}
public bool HasNext()
{
if (position >= items.Length || items[position] == null)
{
return false;
}
else
{
return true;
}
}
public object Next()
{
MenuItem menuItem = items[position];
position += 1;
return menuItem;
}
}
//定义午餐类
public class DinnerMenu : Menu
{
MenuItem[] menuItems;
static int MAX_ITEMS = 6;
int numberOfItem = 0;
public DinnerMenu()
{
menuItems = new MenuItem[MAX_ITEMS];
AddItem("Vegetarian BLT",
"(Fakin') Bacon with lettuce & tomato on whole wheat",
true,
2.99);
AddItem("BLT",
"Bacon with lettuce & tomato on whole wheat",
false,
2.99);
AddItem("Soup of the day",
"Soup of the day, with a side of potato salad",
false,
3.29);
AddItem("Hotdog",
"A hot dog with saurkraut, relish, onions, topped with cheese",
false,
3.05);
AddItem("Steamed Veggies and Brown Rice",
"Steamed vegetables over brown rice",
true,
3.99);
AddItem("Pasta",
"Spaghetti with Marina Sauce and a slice of sourdough bread",
true,
3.89);
}
//
public void AddItem(string name, string description,
bool isVegetarian, double price)
{
MenuItem menuItem = new MenuItem(name, description,
isVegetarian, price);
if (numberOfItem >= MAX_ITEMS)
{
Console.WriteLine("Sorry, menu is full! Can't add item to menu");
}
else
{
menuItems[numberOfItem] = menuItem;
numberOfItem += 1;
}
}
public Iterator CreateIterator()
{
return new DinnerMenuIterator(menuItems);
}
}
//服务员类
public class Waitress
{
Menu dinnerMenu;
Menu cafeMenu;
public Waitress(Menu dinnerMenu, Menu cafeMenu)
{
this.cafeMenu = cafeMenu;
this.dinnerMenu = dinnerMenu;
}
public string PrintMenu()
{
StringBuilder sb = new StringBuilder();
Iterator dinnerIterator = dinnerMenu.CreateIterator();
Iterator cafeIterator = cafeMenu.CreateIterator();
sb.Append("\nLUNCH\n");
sb.Append(PrintMenu(dinnerIterator));
sb.Append("\nDinner\n");
sb.Append(PrintMenu(cafeIterator));
return sb.ToString();
}
public string PrintMenu(Iterator iterator)
{
StringBuilder sb = new StringBuilder();
while (iterator.HasNext())
{
MenuItem menuItem = (MenuItem)iterator.Next();
sb.Append(menuItem.Name + ", ");
sb.Append(menuItem.Price + " -- ");
sb.Append(menuItem.Description + "\n");
}
return sb.ToString();
}
}
//测试示例
public class IteratorTest
{
public static void Main()
{
Menu dinner = new DinnerMenu();
Menu cafe = new CafeMenu();
Waitress wait = new Waitress(dinner, cafe);
Console.WriteLine(wait.PrintMenu());
}
}
