CSharp: Iterator Pattern in donet core 3

 

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#region Iterator   /// <summary> /// 迭代器模式 Iterator Pattern /// geovindu,Geovin Du edit /// </summary> public interface IIterator {     /// <summary>     /// Reset to first element     /// 第一     /// </summary>       void First();     /// <summary>     /// Get next element     /// 下一个     /// </summary>     /// <returns></returns>     string Next();     /// <summary>     /// End of collection check     /// 是否最生     /// </summary>     /// <returns></returns>     bool IsCollectionEnds();     /// <summary>     /// Retrieve Current Item     /// 是否当前     /// </summary>     /// <returns></returns>     string CurrentItem(); }   /// <summary> ///  Science Iterator ///  科学 /// </summary> public class ScienceIterator : IIterator {     /// <summary>     /// 科目列表     /// </summary>     private LinkedList<string> Subjects;     /// <summary>     /// 位置     /// </summary>     private int position;     /// <summary>     ///     /// </summary>     /// <param name="subjects">输入科目列表</param>     public ScienceIterator(LinkedList<string> subjects)     {         this.Subjects = subjects;         position = 0;     }     /// <summary>     /// 第一个位置，0开始     /// </summary>     public void First()     {         position = 0;     }     /// <summary>     /// 下一个位置，加1     /// </summary>     /// <returns></returns>     public string Next()     {         return Subjects.ElementAt(position++);     }     /// <summary>     /// 是否最后     /// </summary>     /// <returns></returns>     public bool IsCollectionEnds()     {         if (position < Subjects.Count)         {             return false;         }         else         {             return true;         }     }     /// <summary>     /// 当前目录     /// </summary>     /// <returns></returns>     public string CurrentItem()     {         return Subjects.ElementAt(position);     } } /// <summary> ///  Arts Iterator ///  行为艺术 /// </summary> public class ArtsIterator : IIterator {     /// <summary>     /// 科目列表     /// </summary>     private string[] Subjects;     /// <summary>     /// 位置位     /// </summary>     private int position;     /// <summary>     /// 行位艺术构造对象     /// </summary>     /// <param name="subjects">输入科目列表</param>     public ArtsIterator(string[] subjects)     {         this.Subjects = subjects;         position = 0;     }     /// <summary>     /// 第一     /// </summary>     public void First()     {         position = 0;     }     /// <summary>     /// 下一个     /// </summary>     /// <returns></returns>     public string Next()     {         //Console.WriteLine("Currently pointing to the subject: "+ this.CurrentItem());         return Subjects[position++];     }     /// <summary>     /// 是否最后     /// </summary>     /// <returns></returns>     public bool IsCollectionEnds()     {         if (position >= Subjects.Length)         {             return true;         }         else         {             return false;         }     }     /// <summary>     /// 当前     /// </summary>     /// <returns></returns>     public string CurrentItem()     {         return Subjects[position];     } } #endregion   #region Aggregate /// <summary> /// /// </summary> public interface ISubjects {     IIterator CreateIterator(); } /// <summary> /// 科学 /// </summary> public class Science : ISubjects {     /// <summary>     /// 科目列表     /// </summary>     private LinkedList<string> Subjects;     /// <summary>     /// 科学构造对象方法     ///     /// </summary>     public Science()     {         Subjects = new LinkedList<string>();         Subjects.AddFirst("Mathematics 应用数学");         Subjects.AddFirst("Computer Science计算机科学");         Subjects.AddFirst("Physics物理学");         Subjects.AddFirst("Electronics电子学");     }     /// <summary>     /// 创建对象     /// </summary>     /// <returns></returns>     public IIterator CreateIterator()     {         return new ScienceIterator(Subjects);     } } /// <summary> /// 行为艺术 /// </summary> public class Arts : ISubjects {     /// <summary>     /// 科目列表     /// </summary>     private string[] Subjects;     /// <summary>     /// 构造行为艺术对象     /// </summary>     public Arts()     {         Subjects = new[] { "English英语", "History历史", "Geography地理", "Psychology心理学" };     }     /// <summary>     /// 创建一个对象方法     /// </summary>     /// <returns></returns>     public IIterator CreateIterator()     {         return new ArtsIterator(Subjects);     } } #endregion

　　

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/// <summary>   /// 迭代器模式 Iterator Pattern   /// geovindu,Geovin Du edit   /// </summary>   /// <typeparam name="T"></typeparam>   public class Node<T>   {       /// <summary>       ///       /// </summary>       ///       public T Value;       /// <summary>       ///       /// </summary>       public Node<T> Left, Right;       /// <summary>       ///       /// </summary>       public Node<T> Parent;       /// <summary>       ///       /// </summary>       /// <param name="value"></param>       public Node(T value)       {           Value = value;       }       /// <summary>       ///       /// </summary>       /// <param name="value"></param>       /// <param name="left"></param>       /// <param name="right"></param>       public Node(T value, Node<T> left, Node<T> right)       {           Value = value;           Left = left;           Right = right;             left.Parent = right.Parent = this;       }   }   /// <summary>   ///   /// </summary>   /// <typeparam name="T"></typeparam>   public class InOrderIterator<T>   {         /// <summary>       ///       /// </summary>       public Node<T> Current { get; set; }       /// <summary>       ///       /// </summary>       private readonly Node<T> root;       /// <summary>       ///       /// </summary>       private bool yieldedStart;       /// <summary>       ///       /// </summary>       /// <param name="root"></param>       public InOrderIterator(Node<T> root)       {           this.root = Current = root;           while (Current.Left != null)               Current = Current.Left;       }       /// <summary>       ///       /// </summary>       public void Reset()       {           Current = root;           yieldedStart = true;       }       /// <summary>       ///       /// </summary>       /// <returns></returns>       public bool MoveNext()       {           if (!yieldedStart)           {               yieldedStart = true;               return true;           }             if (Current.Right != null)           {               Current = Current.Right;               while (Current.Left != null)                   Current = Current.Left;               return true;           }           else           {               var p = Current.Parent;               while (p != null && Current == p.Right)               {                   Current = p;                   p = p.Parent;               }               Current = p;               return Current != null;           }       }   }     /// <summary>   ///   /// </summary>   /// <typeparam name="T"></typeparam>   public class BinaryTree<T>   {         /// <summary>       ///       /// </summary>       private Node<T> root;       /// <summary>       ///       /// </summary>       /// <param name="root"></param>       public BinaryTree(Node<T> root)       {           this.root = root;       }       /// <summary>       ///       /// </summary>       /// <returns></returns>       public InOrderIterator<T> GetEnumerator()       {           return new InOrderIterator<T>(root);       }       /// <summary>       ///       /// </summary>       public IEnumerable<Node<T>> NaturalInOrder       {           get           {               IEnumerable<Node<T>> TraverseInOrder(Node<T> current)               {                   if (current.Left != null)                   {                       foreach (var left in TraverseInOrder(current.Left))                           yield return left;                   }                   yield return current;                   if (current.Right != null)                   {                       foreach (var right in TraverseInOrder(current.Right))                           yield return right;                   }               }               foreach (var node in TraverseInOrder(root))                   yield return node;           }       }   }

　　

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/// <summary> /// 迭代器模式 Iterator Pattern /// geovindu,Geovin Du edit /// </summary> public static class GeovinDuPrint {       /// <summary>     /// 打印     /// </summary>     /// <param name="iterator"></param>     public static void Print(IIterator iterator)     {         while (!iterator.IsCollectionEnds())         {             Console.WriteLine(iterator.Next());         }     } }

　　

 

调用：

 

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Console.WriteLine("***迭代器模式  Iterator Pattern Demonstration.***");     //For Science     ISubjects subjects= new Science();     IIterator iterator = subjects.CreateIterator();     Console.WriteLine("\nScience subjects科学课程： :");     GeovinDuPrint.Print(iterator);       //For Arts     subjects = new Arts();                iterator = subjects.CreateIterator();     Console.WriteLine("\nArts subjects 艺术课程:");     GeovinDuPrint.Print(iterator);     Console.WriteLine();         //     var root = new Node<int>(1, new Node<int>(2), new Node<int>(3));       // C++ style     var it = new InOrderIterator<int>(root);       while (it.MoveNext())     {         Console.WriteLine(it.Current.Value);         Console.WriteLine(',');     }     Console.WriteLine();       // C# style     var tree = new BinaryTree<int>(root);       Console.WriteLine(string.Join(",", tree.NaturalInOrder.Select(x => x.Value)));       // duck typing!     foreach (var node in tree)         Console.WriteLine(node.Value);         Console.ReadLine();

　　

输出：

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***迭代器模式  Iterator Pattern Demonstration.***   Science subjects科学课程： : Electronics电子学 Physics物理学 Computer Science计算机科学 Mathematics 应用数学   Arts subjects 艺术课程: English英语 History历史 Geography地理 Psychology心理学   2 , 1 , 3 ,   2,1,3 2 1 3