设计模式——4.中介者模式

Posted 2020-12-04 sylvan

中介者模式(Mediator)简介：

用一个中介对象来封装一系列对象的交互。中介者模式是各个对象不再显式的相互引用，从而降低耦合，并且可以独立的改变各个对象之间的交互。

中介者模式结构

Colleague类及其子类：

    public abstract class Colleague
    {
        protected Mediator mediator = null;

        public Colleague(Mediator mediator) {
            this.mediator = mediator;
        }

        public abstract void request(string msg);
    }

    public class Colleague1 : Colleague
    {
        public Colleague1(Mediator mediator) : base(mediator) { }

        public void echo(string msg) {
            Console.WriteLine("Colleague1 got the msg : "+msg);
        }

        public override void request(string msg)
        {
            mediator.sendMsg(this,msg);
        }
    }

    public class Colleague2 : Colleague
    {
        public Colleague2(Mediator mediator) : base(mediator) { }

        public void echo(string msg) {
            Console.WriteLine("Colleague2 got the msg : " + msg);
        }

        public override void request(string msg)
        {
            mediator.sendMsg(this,msg);
        }
    }

中介者类：

    public abstract class Mediator
    {
        public abstract void sendMsg(Colleague colleague,string msg);
    }

    public class TheMediator : Mediator
    {
        public Colleague1 C1{ get; set; }
        public Colleague2 C2 { get; set; }
        public override void sendMsg(Colleague colleague, string msg)
        {
            if (colleague == C1)
            {
                C2.echo(msg);
            }
            else {
                C1.echo(msg);
            }
        }
    }

客户端测试代码：

    class Program
    {
        static void Main(string[] args)
        {
            TheMediator theMediator = new TheMediator();
            Colleague1 colleague1 = new Colleague1(theMediator);
            Colleague2 colleague2 = new Colleague2(theMediator);
            theMediator.C1 = colleague1;
            theMediator.C2 = colleague2;

            colleague1.request("Are you OK?");
            colleague2.request("I'm OK!");

            Console.ReadKey();
            
        }
    }

中介者模式的优点及缺点

优点：

使用中介者模式之后，使用的类无论是从类外部获取信息还是向外部传递信息，都通过中介者类来完成；当需要做出一些修改时，可以大大减小后期修改维护时的难度。

缺点：

当过多的类都通过中介者进行沟通时，中介者类中会出现操作接口爆炸的情况，此时，我们可以适当搭配其他设计模式来减轻中介者类的负担。