C# 设计模式（17）迭代器模式

迭代器模式

1. Yield Return

2. 提供统一的访问方式

代码实现：

食品类：

   public  class Food
    {
        public int Id { get; set; }
        public string Name { get; set; }
        public int Price { get; set; }
    }

菜单类：

    public class KFCMenu
    {
        private readonly Food[] _foodArray = new Food[3];

        public KFCMenu()
        {
            _foodArray[0]= new Food()
            {
                Id =01,
                Name = "hamburger",
                Price = 15
            };
            _foodArray[1] = new Food()
            {
                Id = 02,
                Name = "fries",
                Price = 5
            };
            _foodArray[2] = new Food()
            {
                Id = 03,
                Name = "Cola",
                Price = 10
            };
        }

        public Food[] GetFoods()
        {
            return _foodArray;
        }
    }
   public class MacDonaldMenu
    {
        private readonly List<Food> _foodArray = new List<Food>();

        public MacDonaldMenu()
        {
            _foodArray.Add(new Food()
            {
                Id = 01,
                Name = "ketchup",
                Price = 10
            });
            _foodArray.Add(new Food()
            {
                Id = 01,
                Name = "big Mac",
                Price = 20
            });
            _foodArray.Add(new Food()
            {
                Id = 01,
                Name = "Apple Pie",
                Price = 15
            });
        }

        public List<Food> GetFoods()
        {
            return _foodArray;
        }
    }

自定义迭代器：

namespace IteratorPattern.Iterator
{
    public interface IIterator
    {
        bool MoveNext();

        object Current { get; }

        void Reset();
    }
   public class KFCIterator:IIterator
    {
        private readonly KFCMenu _kfcMenu;

        public KFCIterator(KFCMenu kfcMenu)
        {
            _kfcMenu = kfcMenu;
        }

        private int _index = -1;

        public bool MoveNext()
        {
            return _kfcMenu.GetFoods().Length > (++_index);
        }

        public object Current => _kfcMenu.GetFoods()[_index];

        public void Reset()
        {
            _index = -1;
        }
    }
    public class MacDonaldIterator:IIterator
    {
        private readonly MacDonaldMenu _macDonaldMenu;

        public MacDonaldIterator(MacDonaldMenu macDonaldMenu)
        {
            _macDonaldMenu = macDonaldMenu;
        }

        private int _index = -1;

        public bool MoveNext()
        {
            return _macDonaldMenu.GetFoods().Count > (++_index);
        }

        public object Current => _macDonaldMenu.GetFoods()[_index];

        public void Reset()
        {
            _index = -1;
        }
    }
}

代码调用：

    class Program
    {
        static void Main(string[] args)
        {
            KFCMenu kfcMenu = new KFCMenu();
            //.NET Iterator
            Food[] kfcFoods = kfcMenu.GetFoods();
            foreach (var kfcFood in kfcFoods)
            {
                Console.WriteLine($"KFC Menu include {kfcFood.Name},price is {kfcFood.Price} RMB.");
            }

            //Custom Iterator
            KFCIterator kfcIterator = new KFCIterator(kfcMenu);
            while (kfcIterator.MoveNext())
            {
                Console.WriteLine(
                    $"Custom Iterator KFC Menu include {((Food) kfcIterator.Current).Name},price is {((Food) kfcIterator.Current).Price} RMB.");
            }

            MacDonaldMenu macDonaldMenu = new MacDonaldMenu();
            //.NET Iterator
            List<Food> macDonaldFoods = macDonaldMenu.GetFoods();

            foreach (var macDonaldFood in macDonaldFoods)
            {
                Console.WriteLine($"MacDonald Menu include {macDonaldFood.Name},price is {macDonaldFood.Price} RMB.");
            }

            //Custom Iterator
            MacDonaldIterator macDonaldIterator = new MacDonaldIterator(macDonaldMenu);
            while (macDonaldIterator.MoveNext())
            {
                Console.WriteLine(
                    $"Custom Iterator MacDonald Menu include {((Food) macDonaldIterator.Current).Name},price is {((Food) macDonaldIterator.Current).Price} RMB.");
            }
        }
    }

结果：