js备忘录模式 总结
备忘录（Memento）：在不破坏封装的前提下，捕获一个对象的内部状态，并在该对象之外保存这个状态。这样以后就可将该对象恢复到原先保存的状态。
- 备忘录模式比较适用于功能比较复杂的，但需要维护或记录属性历史的类，或者需要保存的属性只是众多属性中的一小部分时，Originator可以根据保存的Memento信息还原到前一状态。
- 如果在某个系统中使用命令模式时，需要实现命令的撤销功能，那么命令模式可以使用备忘录模式来存储可撤销操作的状态。
- 使用备忘录可以把复杂的对象内部信息对其他的对象屏蔽起来，当角色的状态改变的时候，有可能这个状态无效，这时候就可以使用暂时存储起来的备忘录将状态复原。
介绍完备忘录模式的定义之后，下面具体看看备忘录模式的结构图：
备忘录模式中主要有三类角色：
- 发起人角色：记录当前时刻的内部状态，负责创建和恢复备忘录数据。
- 备忘录角色：负责存储发起人对象的内部状态，在进行恢复时提供给发起人需要的状态。
- 管理者角色：负责保存备忘录对象。
C#备忘录模式-单个存储点：
namespace 备忘录模式_单个存储点 { class Program { static void Main(string[] args) { //大战Boss前 GameRole lixiaoyao = new GameRole(); lixiaoyao.GetInitState(); lixiaoyao.StateDisplay(); //保存进度 RoleStateCaretaker stateAdmin = new RoleStateCaretaker(); stateAdmin.Memento = lixiaoyao.SaveState(); //大战Boss时，损耗严重 lixiaoyao.Fight(); lixiaoyao.StateDisplay(); //恢复之前状态 lixiaoyao.RecoveryState(stateAdmin.Memento); lixiaoyao.StateDisplay(); Console.Read(); } } class GameRole { //生命力 private int vit; public int Vitality { get { return vit; } set { vit = value; } } //攻击力 private int atk; public int Attack { get { return atk; } set { atk = value; } } //防御力 private int def; public int Defense { get { return def; } set { def = value; } } //状态显示 public void StateDisplay() { Console.WriteLine("角色当前状态："); Console.WriteLine("体力：{0}", this.vit); Console.WriteLine("攻击力：{0}", this.atk); Console.WriteLine("防御力：{0}", this.def); Console.WriteLine(""); } //保存角色状态 public RoleStateMemento SaveState() { return (new RoleStateMemento(vit, atk, def)); } //恢复角色状态 public void RecoveryState(RoleStateMemento memento) { this.vit = memento.Vitality; this.atk = memento.Attack; this.def = memento.Defense; } //获得初始状态 public void GetInitState() { this.vit = 100; this.atk = 100; this.def = 100; } //战斗 public void Fight() { this.vit = 0; this.atk = 0; this.def = 0; } } //角色状态存储箱 class RoleStateMemento { private int vit; private int atk; private int def; public RoleStateMemento(int vit, int atk, int def) { this.vit = vit; this.atk = atk; this.def = def; } //生命力 public int Vitality { get { return vit; } set { vit = value; } } //攻击力 public int Attack { get { return atk; } set { atk = value; } } //防御力 public int Defense { get { return def; } set { def = value; } } } //角色状态管理者 class RoleStateCaretaker { private RoleStateMemento memento; public RoleStateMemento Memento { get { return memento; } set { memento = value; } } } }
C#备忘录模式-多个存储点：
namespace 备忘录模式_多个存储点 { class Program { static void Main(string[] args) { //大战Boss前 GameRole lixiaoyao = new GameRole(); lixiaoyao.GetInitState(); lixiaoyao.StateDisplay(); //保存进度 RoleStateCaretaker stateAdmin = new RoleStateCaretaker(); stateAdmin.MementoDic.Add(DateTime.Now.ToString(), lixiaoyao.SaveState()); //大战Boss时，损耗严重 lixiaoyao.Fight1(); lixiaoyao.StateDisplay(); //保存进度 Thread.Sleep(1000); stateAdmin.MementoDic.Add(DateTime.Now.ToString(), lixiaoyao.SaveState()); //大战Boss时，损耗严重 lixiaoyao.Fight2(); lixiaoyao.StateDisplay(); //恢复之前状态 Console.WriteLine("-------恢复联系人列表,请从以下列表选择恢复的日期------"); var keyCollection = stateAdmin.MementoDic.Keys; foreach (string k in keyCollection) { Console.WriteLine("Key = {0}", k); } while (true) { Console.Write("请输入数字,按窗口的关闭键退出:"); int index = -1; try { index = Int32.Parse(Console.ReadLine()); } catch { Console.WriteLine("输入的格式错误"); continue; } RoleStateMemento memento = null; if (index < keyCollection.Count && stateAdmin.MementoDic.TryGetValue(keyCollection.ElementAt(index), out memento)) { lixiaoyao.RecoveryState(memento); lixiaoyao.StateDisplay(); } else { Console.WriteLine("输入的索引大于集合长度！"); } } } } class GameRole { //生命力 private int vit; public int Vitality { get { return vit; } set { vit = value; } } //攻击力 private int atk; public int Attack { get { return atk; } set { atk = value; } } //防御力 private int def; public int Defense { get { return def; } set { def = value; } } //状态显示 public void StateDisplay() { Console.WriteLine("角色当前状态："); Console.WriteLine("体力：{0}", this.vit); Console.WriteLine("攻击力：{0}", this.atk); Console.WriteLine("防御力：{0}", this.def); Console.WriteLine(""); } //保存角色状态 public RoleStateMemento SaveState() { return (new RoleStateMemento(vit, atk, def)); } //恢复角色状态 public void RecoveryState(RoleStateMemento memento) { this.vit = memento.Vitality; this.atk = memento.Attack; this.def = memento.Defense; } //获得初始状态 public void GetInitState() { this.vit = 100; this.atk = 100; this.def = 100; } //战斗 public void Fight1() { this.vit = 50; this.atk = 50; this.def = 50; } public void Fight2() { this.vit = 0; this.atk = 0; this.def = 0; } } //角色状态存储箱 class RoleStateMemento { private int vit; private int atk; private int def; public RoleStateMemento(int vit, int atk, int def) { this.vit = vit; this.atk = atk; this.def = def; } //生命力 public int Vitality { get { return vit; } set { vit = value; } } //攻击力 public int Attack { get { return atk; } set { atk = value; } } //防御力 public int Defense { get { return def; } set { def = value; } } } //角色状态管理者 class RoleStateCaretaker { // 使用多个备忘录来存储多个备份点 private Dictionary<string, RoleStateMemento> mementoDic; public Dictionary<string, RoleStateMemento> MementoDic { get { return mementoDic; } set { mementoDic = value; } } public RoleStateCaretaker() { MementoDic = new Dictionary<string, RoleStateMemento>(); } } }
js的备忘录模式-单个存储点：
var GameRole = function(){ //角色状态存储箱 var roleStateMemento = {}; this.getMemento = function(){ return roleStateMemento; }; this.setMemento = function(memento){ roleStateMemento = memento; }; this.getInitState(); }; //状态显示 GameRole.prototype.stateDisplay = function(){ console.log('角色当前状态：'); console.log('体力：' + this.vitality); console.log('攻击力：' + this.attack); console.log('防御力：' + this.defense); }; //保存角色状态 GameRole.prototype.saveState = function(){ this.setMemento({ vitality:this.vitality, attack:this.attack, defense:this.defense }); }; //恢复角色状态 GameRole.prototype.recoveryState = function(){ var memento = this.getMemento(); this.vitality = memento.vitality; this.attack = memento.attack; this.defense = memento.defense; }; //获得初始状态 GameRole.prototype.getInitState = function(){ this.vitality = 100; this.attack = 100; this.defense = 100; }; //战斗 GameRole.prototype.fight = function(){ this.vitality = 0; this.attack = 0; this.defense = 0; }; //调用： // //大战Boss前 var gr = new GameRole(); gr.stateDisplay(); //保存进度 gr.saveState(); //大战Boss时，损耗严重 gr.fight(); gr.stateDisplay(); //恢复之前状态 gr.recoveryState(); gr.stateDisplay();
js的备忘录模式-多个存储点：
var GameRole = function(){ //角色状态存储箱 var roleStateMemento = {}; this.getMemento = function(key){ if(key) return roleStateMemento[key]; else return roleStateMemento; }; this.setMemento = function(key,memento){ roleStateMemento[key] = memento; }; this.getInitState(); }; //状态显示 GameRole.prototype.stateDisplay = function(){ console.log('角色当前状态：'); console.log('体力：' + this.vitality); console.log('攻击力：' + this.attack); console.log('防御力：' + this.defense); }; //保存角色状态 GameRole.prototype.saveState = function(key){ this.setMemento(key,{ vitality:this.vitality, attack:this.attack, defense:this.defense }); }; //恢复角色状态 GameRole.prototype.recoveryState = function(key){ var memento = this.getMemento(key); this.vitality = memento.vitality; this.attack = memento.attack; this.defense = memento.defense; }; //获得初始状态 GameRole.prototype.getInitState = function(){ this.vitality = 100; this.attack = 100; this.defense = 100; }; //战斗 GameRole.prototype.fight1 = function(){ this.vitality = 50; this.attack = 50; this.defense = 50; }; GameRole.prototype.fight2 = function(){ this.vitality = 0; this.attack = 0; this.defense = 0; }; //调用： // //大战Boss前 var gr = new GameRole(); gr.stateDisplay(); //保存进度 gr.saveState(new Date().getTime()); //大战Boss时，损耗严重 gr.fight1(); gr.stateDisplay(); setTimeout(function(){ //保存进度 gr.saveState(new Date().getTime()); //大战Boss时，损耗严重 gr.fight2(); gr.stateDisplay(); var mementos = gr.getMemento(); for(var key in mementos){ console.log('key = ' + key); //恢复之前状态 gr.recoveryState(key); gr.stateDisplay(); } },1000);
备忘录模式主要思想是——利用备忘录对象来对保存发起人的内部状态，当发起人需要恢复原来状态时，再从备忘录对象中进行获取，如果系统需要提供回滚操作时，使用备忘录模式非常合适。例如文本编辑器的Ctrl+Z撤销操作的实现，数据库中事务操作。