js备忘录模式

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);

总结

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。