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