Design Patterns-Memento Pattern

備忘錄模式-在這如果我想做一個遊戲，以RPG來說，在進入遊戲戰鬥時我可以讓玩家選擇重新開始這場戰鬥，就像FFXIII玩家可以在戰鬥中隨時重新挑戰怪物更高分數、不同打法，

那該如何儲存腳色能力?

GameRole.cs:

   1: class GameRole

   2: {

   3:     private int hp;

   4:     public int HP

   5:     {

   6:         set{hp = value;}

   7:         get{return hp;}

   8:     }

   9: }

  10: public void StateDisplay()

  11: {

  12:     Console.WriteLine("Now");

  13:     Console.WriteLine("HP:{0}",this.hp);

  14: }

  15: public void GetInitialize()

  16: {

  17:     this.hp = 100;

  18: }

  19: public void End()

  20: {

  21:     this.hp = 50;

  22: }

  23:  

  24: static void Main(string[] args)

  25: {

  26:   GameRole playerRole = new GameRole();

  27:   

  28:   //Game Initialize

  29:   playerRole.GetInitialize();

  30:   playerRole.StateDisplay();

  31:   

  32:   //Enter a battle : Record Play's Val

  33:   GameRole backup = new GameRole();

  34:   playerRole.HP = backup.HP; //出現物件細節，Not good

  35:  

  36:   //Battle is done

  37:   playRole.End()

  38:   playRole.StateDisplay();

  39:  

  40:  

  41:   // I want Re battle

  42:   playerRole.HP = backup.HP; //出現物件細節，Not good

  43:   playRole.StateDisplay();

  44:   

  45:   Console.Read();

  46: }

Memento Patterns:在不破壞封裝性的前提下，讀取一個物件的內部狀態，並在該物件之外保存這個狀態。可以讓物件回復到原先狀態保存狀態。

PlayerStateManager:根據狀態負責建立PlayerRecordManager，並同時記錄內部狀態，讓它可以用PlayerRecordManager回復狀態，StateManager可以決定RecordManager該存那些值與狀態。

PlayerRecordManager:負責存StateManager所需要的狀態與值，並防止其他物件存取RecordManager。RecordManager有兩個介面:

1.只能看到StateManager的窄介面，只能將值傳遞出去。

2.StateManager可以看到一個寬介面，允許存取恢復到先前的值。

PlayerRecorder:負責保存RecordManager，不能對其做任何檢查或操作。

其PlayerStateManager.cs:

   1: class PlayerStateManager()

   2: {

   3:   private string state;

   4:   public string State

   5:   {

   6:    get{return state;}

   7:    set{state = value;}

   8:   }

   9:   public PlayerRecordManager CreatePlayerRecordManager()

  10:   {

  11:     return (new PlayerRecordManager(state));

  12:   }

  13:   public void SetPlayerRecordManager(PlayerRecordManager recordManager)

  14:   {

  15:    state = recordManager.State;

  16:   }

  17:   public void Show()

  18:   {

  19:    //write out "State="+ state

  20:   }

  21: }

PlayerRecordManager.cs:

   1: class PlayerRecordManager

   2: {

   3:   private string state;

   4:   public PlayerRecordManager(string state)

   5:   {

   6:     this.state = state;

   7:   }

   8:   public string State

   9:   {

  10:    get{return state;}

  11:   }

  12: }PlayerRecorder.cs:

  13:  

  14: class PlayerRecorder

  15: {

  16:   private PlayerRecordManager playerRecordManager;

  17:   

  18:   public PlayerRecordManager PlayerRecordManager

  19:   {

  20:    get{return playerRecordManager;}

  21:    set{playerRecordManager = value;}

  22:   }

  23: }

PlayerRecorder.cs:

   1: class PlayerRecorder

   2: {

   3:   private PlayerRecordManager playerRecordManager;

   4:   

   5:   public PlayerRecordManager PlayerRecordManager

   6:   {

   7:    get{return playerRecordManager;}

   8:    set{playerRecordManager = value;}

   9:   }

  10: }

---

保存細節的目的是為了將細節封裝後，當需要更改保存細節時也不會影響到客戶端。

適用:

1.功能比較複雜但需要維護或記錄屬性歷史的類別。

2.需要保存的屬性只是眾多屬性中的一小部分，PlayerStateManager可以根據保存的PlayerRecordManager資訊還原到前一狀態。

缺點:
1.如果狀態資料很大量，在資源消耗上會非常耗記憶體。

---

   1: class PlayerStateManager()

   2: {

   3:   //........

   4:   public PlayerRecordManager SaveState()

   5:   {

   6:     return (new PlayerRecordManager(hp));

   7:   }

   8:   public void RecovertState(PlayerRecordManager recordManager)

   9:   {

  10:    this.hp = recordManager.HP;

  11:   }

  12:   //..........

  13: }

   1: class PlayerRecordManager

   2: {

   3:   private int hp;

   4:   public PlayerRecordManager(int hp)

   5:   {

   6:     this.hp = hp;

   7:   }

   8:   public int HP

   9:   {

  10:    set{hp = value;}

  11:    get{return hp;}

  12:   }

  13: }

   1: class PlayerRecorder

   2: {

   3:   private PlayerRecordManager playerRecordManager;

   4:   

   5:   public PlayerRecordManager PlayerRecordManager

   6:   {

   7:    get{return playerRecordManager;}

   8:    set{playerRecordManager = value;}

   9:   }

  10: }

   1: static void Main(string[] args)

   2: {

   3:   PlayerStateManager player =  new PlayerStateManager();

   4:   

   5:   player.GetInitState();

   6:   player.StateDisplay();

   7:  

   8:   //Backup State

   9:   PlayerRecorder stateAdmin = new PlayerRecorder();

  10:   stateAdmin.PlayerRecordManager = player.SaveState();

  11:   

  12:   player.End();

  13:   player.StateDisplay();

  14:    

  15:   player.RecoveryState(stateAdmin.PlayerRecordManager);

  16:   player.stateDisplay();

  17:   Console.Read();

  18: }