設計模式（20）---中介者模式

2019-11-14 16:17:39

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一、定義

中介者模式：用一個中介對象來封裝一系列的對象交互。中介者使對象不需要顯式地相互引用，從而使其耦合松散，而且可以獨立地改變它們之間的交互。

解釋：通俗來講，有多個對象，它們相互之間有交互。現在為了降低它們的耦合度，提供一個中介者，相當于第三方，各個對象都通過第三方來進行相互間的邏輯操作。

二、UML類圖及基本代碼

基本代碼：

abstract class Mediator    {        public abstract void Send(string message, Colleague colleague);    }    class ConcreteMediator : Mediator    {        PRivate ConcreteColleage1 colleague1;        private ConcreteColleage2 colleague2;        public ConcreteColleage1 Colleague1        {            set { colleague1 = value; }        }        public ConcreteColleage2 Colleague2        {            set { colleague2 = value; }        }        public override void Send(string message, Colleague colleague)        {            if (colleague == colleague1)            {                colleague2.Receive(message);            }            else            {                colleague1.Receive(message);            }        }    }    abstract class Colleague    {        protected Mediator mediator;        public Colleague(Mediator mediator)        {            this.mediator = mediator;        }    }    class ConcreteColleage1 : Colleague    {        public ConcreteColleage1(Mediator mediator)            : base(mediator)        { }        public void Send(string message)        {            mediator.Send(message, this);        }        public void Receive(string message)        {            Console.WriteLine("同事1得到信息：" + message);        }    }    class ConcreteColleage2 : Colleague    {        public ConcreteColleage2(Mediator mediator)            : base(mediator)        { }        public void Send(string message)        {            mediator.Send(message, this);        }        public void Receive(string message)        {            Console.WriteLine("同事2得到信息：" + message);        }    }

客戶端調用及其結果：

ConcreteMediator mediator = new ConcreteMediator();            ConcreteColleage1 c1 = new ConcreteColleage1(mediator);            ConcreteColleage2 c2 = new ConcreteColleage2(mediator);            mediator.Colleague1 = c1;            mediator.Colleague2 = c2;            c1.Send("吃飯了嗎？");            c2.Send("還沒有，你打算請客？");

三、具體實例

A和B博弈，A贏則B會輸，反之亦然。假設A和B開始時都要20塊錢，基本代碼如下：

首先構造抽象中介者類和具體中介者類：

public abstract class AbstractMediator    {        public abstract void AWin(int count);        public abstract void BWin(int count);    }    public class MediatorPater : AbstractMediator    {        private ParterA a;        private ParterB b;        public ParterA A        {            set { a = value; }        }        public ParterB B        {            set { b = value; }        }        public override void AWin(int count)        {            a.MoneyCount += count;            b.MoneyCount -= count;        }        public override void BWin(int count)        {            b.MoneyCount += count;            a.MoneyCount -= count;        }    }

接著編寫抽象對弈者，構造具體的對弈者A和B：

public abstract class AbstractCardPartner    {        public int MoneyCount { get; set; }        public AbstractCardPartner()        {            MoneyCount = 0;        }        public abstract void ChangeCount(int count, AbstractMediator mediator);    }    public class ParterA : AbstractCardPartner    {        public override void ChangeCount(int Count, AbstractMediator mediator)        {            mediator.AWin(Count);        }    }    public class ParterB : AbstractCardPartner    {        public override void ChangeCount(int Count, AbstractMediator mediator)        {            mediator.BWin(Count);        }    }

客戶端調用代碼及其結果：

MediatorPater mediator = new MediatorPater();            ParterA partA = new ParterA();            ParterB partB = new ParterB();            mediator.A = partA;            mediator.B = partB;            partA.MoneyCount = 20;            partB.MoneyCount = 20;            partA.ChangeCount(7, mediator);            Console.WriteLine("A 現在的錢是：{0}", partA.MoneyCount);            Console.WriteLine("B 現在的錢是：{0}", partB.MoneyCount);             partB.ChangeCount(11, mediator);            Console.WriteLine("A 現在的錢是：{0}", partA.MoneyCount);            Console.WriteLine("B 現在的錢是：{0}", partB.MoneyCount);