CSharp: Memento Pattern in donet core 3

 

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/// <summary> ///  备忘录模式 Memento Pattern  亦称： 快照、Snapshot、Memento ///  geovindu,Geovin Du edit /// </summary>    class Originator {       /// <summary>     /// 状态     /// </summary>     private string state;     /// <summary>     /// Memento myMemento;//not needed now     /// </summary>     public Originator()     {         //Creating a memento with born state.         state = "快照 #0.(出生状态)";         Console.WriteLine($"发起人的当前状态是: {state}");       }     /// <summary>     /// 状态     /// </summary>     public string State     {         get { return state; }         set         {             state = value;             Console.WriteLine($"发起人的的当前状态是: {state}");         }     }         /// <summary>     ///     /// </summary>     /// <returns></returns>     public Memento CurrentMemento()     {         //Code segment used in Demonstration-1         //myMemento = new Memento();//error now, because of private constructor         //myMemento.State = state;         //return myMemento;           //Modified code for Demonstration-2         return new Memento(this.State);     }       /// <summary>     /// Back to an old state (Restore)     /// </summary>     /// <param name="restoreMemento"></param>     public void RestoreMemento(Memento restoreMemento)     {         this.state = restoreMemento.State;         //Console.WriteLine("Restored to state : {0}", state);         Console.WriteLine($"愎复状态是: {state}");     }     /// <summary>     /// Memento class     /// </summary>     internal class Memento            {         /// <summary>         ///         /// </summary>         private string state;         //Now Memento class cannot be initialized outside         /// <summary>         ///         /// </summary>         private Memento() { }         /// <summary>         ///         /// </summary>         /// <param name="state">输入状态</param>         public Memento(string state)         {             this.state = state;         }         /// <summary>         ///         /// </summary>         public string State         {             get             {                 return state;             }             set             {                 state = value;             }         }     }   }

　　

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/// <summary>   ///  备忘录模式 Memento Pattern  亦称： 快照、Snapshot、Memento   ///  geovindu,Geovin Du edit   /// </summary>   public class Memento   {         /// <summary>       ///       /// </summary>       public int Balance { get; }       /// <summary>       ///       /// </summary>       /// <param name="balance"></param>       public Memento(int balance)       {           Balance = balance;       }   }   /// <summary>   ///   /// </summary>   public class BankAccount // supports undo/redo   {       /// <summary>       ///       /// </summary>       private int balance;       /// <summary>       ///       /// </summary>       private List<Memento> changes = new List<Memento>();       /// <summary>       ///       /// </summary>       private int current;       /// <summary>       ///       /// </summary>       /// <param name="balance"></param>       public BankAccount(int balance)       {           this.balance = balance;           changes.Add(new Memento(balance));       }       /// <summary>       ///       /// </summary>       /// <param name="amount"></param>       /// <returns></returns>       public Memento Deposit(int amount)       {           balance += amount;           var m = new Memento(balance);           changes.Add(m);           ++current;           return m;       }       /// <summary>       ///       /// </summary>       /// <param name="m"></param>       public void Restore(Memento m)       {           if (m != null)           {               balance = m.Balance;               changes.Add(m);               current = changes.Count - 1;           }       }       /// <summary>       ///       /// </summary>       /// <returns></returns>       public Memento Undo()       {           if (current > 0)           {               var m = changes[--current];               balance = m.Balance;               return m;           }           return null;       }       /// <summary>       ///       /// </summary>       /// <returns></returns>       public Memento Redo()       {           if (current + 1 < changes.Count)           {               var m = changes[++current];               balance = m.Balance;               return m;           }           return null;       }       /// <summary>       ///       /// </summary>       /// <returns></returns>       public override string ToString()       {           return $"{nameof(balance)}: {balance}";       }   }

　　

调用：

 

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//备忘录模式         Originator originatorObject;         Originator.Memento currentMemento;          Console.WriteLine("***备忘录模式Memento Pattern Demonstration-2.***");        Console.WriteLine("发起人 (带有嵌套的内部类“Memento”)在一个单独的文件中维护.\n");          originatorObject = new Originator();                       IList<Originator.Memento> savedStates = new List<Originator.Memento>();        /*         Adding a memento the list.This memento stores         the current state of the Origintor.        */        savedStates.Add(originatorObject.CurrentMemento());          //Snapshot #1.        originatorObject.State = "快照 #1";        //Adding this memento as a  restore point                   savedStates.Add(originatorObject.CurrentMemento());            //Snapshot #2.        originatorObject.State = "快照 #2";        //Adding this memento as a  restore point                   savedStates.Add(originatorObject.CurrentMemento());          //Snapshot #3.        originatorObject.State = "快照 #3";        //Adding this memento as a  restore point                   savedStates.Add(originatorObject.CurrentMemento());          //Snapshot #4. It is not added as a restore point.        originatorObject.State = "快照 #4";          //Available restore points        Console.WriteLine("\n当前可用的恢复点为 :");        foreach (Originator.Memento m in savedStates)        {            Console.WriteLine(m.State);        }          //Undo's        //Roll back starts...                   Console.WriteLine("\n现在执行撤销.");        for (int i = savedStates.Count; i > 0; i--)        {            //Get a restore point            currentMemento = savedStates[i - 1];            originatorObject.RestoreMemento(currentMemento);        }        //Redo's        Console.WriteLine("\n现在执行重做.");        for (int i = 1; i < savedStates.Count; i++)        {            currentMemento = savedStates[i];            originatorObject.RestoreMemento(currentMemento);        }          Console.WriteLine();          var ba = new BankAccount(100);        ba.Deposit(50);        ba.Deposit(25);        Console.WriteLine(ba);          ba.Undo();        Console.WriteLine($"Undo geovindu #1: {ba}");        ba.Undo();        Console.WriteLine($"Undo geovindu #2: {ba}");        ba.Redo();        Console.WriteLine($"Redo geovindu #2: {ba}");            Console.ReadKey();

　　

输出：

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***备忘录模式Memento Pattern Demonstration-2.*** 发起人 (带有嵌套的内部类“Memento”)在一个单独的文件中维护.   发起人的当前状态是: 快照 #0.(出生状态) 发起人的的当前状态是: 快照 #1 发起人的的当前状态是: 快照 #2 发起人的的当前状态是: 快照 #3 发起人的的当前状态是: 快照 #4   当前可用的恢复点为 : 快照 #0.(出生状态) 快照 #1 快照 #2 快照 #3   现在执行撤销. 愎复状态是: 快照 #3 愎复状态是: 快照 #2 愎复状态是: 快照 #1 愎复状态是: 快照 #0.(出生状态)   现在执行重做. 愎复状态是: 快照 #1 愎复状态是: 快照 #2 愎复状态是: 快照 #3   balance: 175 Undo geovindu #1: balance: 150 Undo geovindu #2: balance: 100 Redo geovindu #2: balance: 150