设计模式(16)中介者模式
模式介绍
中介器设计模式定义了一个对象,该对象封装了一组对象之间如何相互作用。
示例
我们想象一下电影院的快餐柜,电影院有多个区域都有这样的快餐柜,我们来设计一个它们之间交流的系统。
中介者接口:
/// <summary>
/// The Mediator interface, which defines a send message method which the concrete mediators must implement.
/// </summary>
interface Mediator
{
void SendMessage(string message, ConcessionStand concessionStand);
}
抽象的柜台:
/// <summary>
/// The Colleague abstract class, representing an entity involved in the conversation which should receive messages.
/// </summary>
abstract class ConcessionStand
{
protected Mediator mediator;
public ConcessionStand(Mediator mediator)
{
this.mediator = mediator;
}
}
具体的柜台:
/// <summary>
/// A Concrete Colleague class
/// </summary>
class NorthConcessionStand : ConcessionStand
{
// Constructor
public NorthConcessionStand(Mediator mediator) : base(mediator)
{
}
public void Send(string message)
{
Console.WriteLine("North Concession Stand sends message: " + message);
mediator.SendMessage(message, this);
}
public void Notify(string message)
{
Console.WriteLine("North Concession Stand gets message: " + message);
}
}
/// <summary>
/// A Concrete Colleague class
/// </summary>
class SouthConcessionStand : ConcessionStand
{
public SouthConcessionStand(Mediator mediator) : base(mediator)
{
}
public void Send(string message)
{
Console.WriteLine("South Concession Stand sends message: " + message);
mediator.SendMessage(message, this);
}
public void Notify(string message)
{
Console.WriteLine("South Concession Stand gets message: " + message);
}
}
具体的中介者:
/// <summary>
/// The Concrete Mediator class, which implement the send message method and keep track of all participants in the conversation.
/// </summary>
class ConcessionsMediator : Mediator
{
private NorthConcessionStand _northConcessions;
private SouthConcessionStand _southConcessions;
public NorthConcessionStand NorthConcessions
{
set { _northConcessions = value; }
}
public SouthConcessionStand SouthConcessions
{
set { _southConcessions = value; }
}
public void SendMessage(string message, ConcessionStand colleague)
{
if (colleague == _northConcessions)
{
_southConcessions.Notify(message);
}
else
{
_northConcessions.Notify(message);
}
}
}
客户端调用:
static void Main(string[] args)
{
ConcessionsMediator mediator = new ConcessionsMediator();
NorthConcessionStand leftKitchen = new NorthConcessionStand(mediator);
SouthConcessionStand rightKitchen = new SouthConcessionStand(mediator);
mediator.NorthConcessions = leftKitchen;
mediator.SouthConcessions = rightKitchen;
leftKitchen.Send("Can you send some popcorn?");
rightKitchen.Send("Sure thing, Kenny's on his way.");
rightKitchen.Send("Do you have any extra hot dogs? We've had a rush on them over here.");
leftKitchen.Send("Just a couple, we'll send Kenny back with them.");
Console.ReadKey();
}
总结
中介者使中介人“站在”通信对象之间,控制他们的通信。常用于聊天系统。
源代码
https://github.com/exceptionnotfound/DesignPatterns/tree/master/Mediator
原文
https://www.exceptionnotfound.net/mediator-the-daily-design-pattern/