设计模式22：Mediator Pattern (调解者模式)

英文原文：http://www.dofactory.com/Patterns/PatternMediator.aspx

一、Mediator Pattern (调解者模式)的定义

Define an object that encapsulates how a set of objects interact. Mediator promotes loose coupling by keeping objects from referring to each other explicitly, and it lets you vary their interaction independently.

定义一个对象将一系列对象如何相互作用的操作进行封装。调解者通过避免一个对象明确指向其余的对象来促使自由耦合，同时能够让你单独的改变他们之间的相互作用。

二、UML类图

Mediator  (IChatroom)

• 定义一个接口用于与同事级对象进行通信

ConcreteMediator  (Chatroom)

• 通过与同事级对象进行对等来实现相互协作行为
• 知道并且维持本身的同事级对象

Colleague classes  (Participant)

• 每个同事级对象都知道自己的调节者对象
• 每个同事级对象在与另外的同事级对象进行通信时必须要与调节者进行通信。

三、调解者模式实例代码

using System; using System.Collections.Generic; using System.Linq; using System.Text; namespace Mediator_Pattern { /// <summary> /// MainApp startup class for Structural /// Mediator Design Pattern. /// </summary> class MainApp { /// <summary> /// Entry point into console application. /// </summary> static void Main() { ConcreteMediator m = new ConcreteMediator(); ConcreteColleague1 c1 = new ConcreteColleague1(m); ConcreteColleague2 c2 = new ConcreteColleague2(m); m.Colleague1 = c1; m.Colleague2 = c2; c1.Send("How are you?"); c2.Send("Fine, thanks"); // Wait for user Console.ReadKey(); } } /// <summary> /// The 'Mediator' abstract class /// </summary> abstract class Mediator { public abstract void Send(string message, Colleague colleague); } /// <summary> /// The 'ConcreteMediator' class /// </summary> class ConcreteMediator : Mediator { private ConcreteColleague1 _colleague1; private ConcreteColleague2 _colleague2; public ConcreteColleague1 Colleague1 { set { _colleague1 = value; } } public ConcreteColleague2 Colleague2 { set { _colleague2 = value; } } public override void Send(string message, Colleague colleague) { if (colleague == _colleague1) { _colleague2.Notify(message); } else { _colleague1.Notify(message); } } } /// <summary> /// The 'Colleague' abstract class /// </summary> abstract class Colleague { protected Mediator mediator; // Constructor public Colleague(Mediator mediator) { this.mediator = mediator; } } /// <summary> /// A 'ConcreteColleague' class /// </summary> class ConcreteColleague1 : Colleague { // Constructor public ConcreteColleague1(Mediator mediator) : base(mediator) { } public void Send(string message) { mediator.Send(message, this); } public void Notify(string message) { Console.WriteLine("Colleague1 gets message: " + message); } } /// <summary> /// A 'ConcreteColleague' class /// </summary> class ConcreteColleague2 : Colleague { // Constructor public ConcreteColleague2(Mediator mediator) : base(mediator) { } public void Send(string message) { mediator.Send(message, this); } public void Notify(string message) { Console.WriteLine("Colleague2 gets message: " + message); } } }

四、另外一个使用调解者模式的实例代码

This real-world code demonstrates the Mediator pattern facilitating loosely coupled communication between different Participants registering with a Chatroom. The Chatroom is the central hub through which all communication takes place. At this point only one-to-one communication is implemented in the Chatroom, but would be trivial to change to one-to-many.

using System; using System.Collections.Generic; using System.Linq; using System.Text; namespace Mediator_Pattern { /// <summary> /// MainApp startup class for Real-World /// Mediator Design Pattern. /// </summary> class MainApp { /// <summary> /// Entry point into console application. /// </summary> static void Main() { // Create chatroom Chatroom chatroom = new Chatroom(); // Create participants and register them Participant George = new Beatle("George"); Participant Paul = new Beatle("Paul"); Participant Ringo = new Beatle("Ringo"); Participant John = new Beatle("John"); Participant Yoko = new NonBeatle("Yoko"); chatroom.Register(George); chatroom.Register(Paul); chatroom.Register(Ringo); chatroom.Register(John); chatroom.Register(Yoko); // Chatting participants Yoko.Send("John", "Hi John!"); Paul.Send("Ringo", "All you need is love"); Ringo.Send("George", "My sweet Lord"); Paul.Send("John", "Can't buy me love"); John.Send("Yoko", "My sweet love"); // Wait for user Console.ReadKey(); } } /// <summary> /// The 'Mediator' abstract class /// </summary> abstract class AbstractChatroom { public abstract void Register(Participant participant); public abstract void Send( string from, string to, string message); } /// <summary> /// The 'ConcreteMediator' class /// </summary> class Chatroom : AbstractChatroom { private Dictionary<string, Participant> _participants = new Dictionary<string, Participant>(); public override void Register(Participant participant) { if (!_participants.ContainsValue(participant)) { _participants[participant.Name] = participant; } participant.Chatroom = this; } public override void Send( string from, string to, string message) { Participant participant = _participants[to]; if (participant != null) { participant.Receive(from, message); } } } /// <summary> /// The 'AbstractColleague' class /// </summary> class Participant { private Chatroom _chatroom; private string _name; // Constructor public Participant(string name) { this._name = name; } // Gets participant name public string Name { get { return _name; } } // Gets chatroom public Chatroom Chatroom { set { _chatroom = value; } get { return _chatroom; } } // Sends message to given participant public void Send(string to, string message) { _chatroom.Send(_name, to, message); } // Receives message from given participant public virtual void Receive( string from, string message) { Console.WriteLine("{0} to {1}: '{2}'", from, Name, message); } } /// <summary> /// A 'ConcreteColleague' class /// </summary> class Beatle : Participant { // Constructor public Beatle(string name) : base(name) { } public override void Receive(string from, string message) { Console.Write("To a Beatle: "); base.Receive(from, message); } } /// <summary> /// A 'ConcreteColleague' class /// </summary> class NonBeatle : Participant { // Constructor public NonBeatle(string name) : base(name) { } public override void Receive(string from, string message) { Console.Write("To a non-Beatle: "); base.Receive(from, message); } } }