1、观察者模式概念
观察者模式定义了一种一对多的依赖关系，让多个观察者对象同时监听某一个主题对象，这个主题对象在状态发生变化时，会通知所有观察者对象，使它们能够自动更新自己的行为。
观察者模式实现了表示层和数据逻辑层的分离，并定义了稳定的更新消息传递机制，并抽象了更新接口，使得可以有各种各样不同的表示层，即观察者。
观察者模式在被观察者和观察者之间建立了一个抽象的耦合，被观察者并不知道任何一个具体的观察者，只是保存着抽象观察者的列表，每个具体观察者都符合一个抽象观察者的接口。
2、业务场景
模拟管理系统推送最新讯息给对应用户，采用观察者模式将很好的模拟此类场景，使发布者与订阅者之间实现解耦。
3、实战
3.1 定义实体对象
定义订阅者实体类
namespace SubscriberDesignWithRedis.Model{public class User{/// <summary>/// 用户id/// </summary>public string userId { get; set; }/// <summary>/// 用户名称/// </summary>public string userName { get; set; }}}
此处List<User> 用于存储订阅者列表
namespace SubscriberDesignWithRedis.Model{[Serializable]public class Information{/// <summary>/// 发布者集合/// </summary>public List<User> userList{ get; set; }/// <summary>/// 信号/// </summary>public string signal { get; set; }/// <summary>/// 消息/// </summary>public string info { get; set; }}}
3.2 发布者
/// <summary>/// 门户发布信息/// </summary>public class PortalPublish{/// <summary>/// 定义委托方法，充当订阅者接口/// </summary>/// <param name="obj"></param>public delegate void NotifySubscribeEventHandler(object obj);/// <summary>/// 发布消息内部类/// </summary>public class PublishInfo{public NotifySubscribeEventHandler notifyEvent;/// <summary>/// 消息实体/// </summary>public Information Information { get; set; }/// <summary>/// 重载构造器/// </summary>/// <param name="information">消息实体</param>public PublishInfo(Information information){this.Information = information;}/// <summary>/// 新增/// </summary>/// <param name="ob"></param>public void AddSubscribe(NotifySubscribeEventHandler ob){notifyEvent += ob;}/// <summary>/// 删除/// </summary>/// <param name="ob"></param>public void RemoveSubscribe(NotifySubscribeEventHandler ob){notifyEvent -= ob;}/// <summary>/// 更新( 使用lamda表达式 )/// </summary>public void Update() => notifyEvent?.Invoke(this);}public class PortalPublishInfo : PublishInfo{public PortalPublishInfo(Information information) : base(information) { }}}
3.3 订阅者
namespace SubscriberDesignWithRedis{public class Subscriber{public string Name { get; set; }public Subscriber(string name){this.Name = name;}/// <summary>/// 接收/// </summary>/// <param name="obj"></param>public void Recevie(object obj){PortalPublish.PortalPublishInfo portalPublishInfo = obj as PortalPublish.PortalPublishInfo;if(portalPublishInfo != null){Console.WriteLine("Notified {0} of {1}'s " + "Info is :{2}", Name,
portalPublishInfo.Information.signal, portalPublishInfo.Information.info);}}}}
3.4 测试类
namespace SubscriberDesignWithRedis{class Program{static void Main(string[] args){//模拟订阅者的集合List<User> userList = new List<User>() {new User() { userId = "1", userName = "ozil" },new User() { userId = "2",userName = "Alexis"}};//定义发布数据Information information = new Information() {signal = "Publish Info",info = "this is a new information for each client",userList = userList};PortalPublishInfo portalPublish = new PortalPublishInfo(information);Console.WriteLine("添加订阅者");//循环订阅者列表，将消息发送给具体订阅者foreach (User user in userList){Subscriber client = new Subscriber(user.userName);portalPublish.AddSubscribe(new NotifySubscribeEventHandler(client.Recevie));}//执行事件 portalPublish.Update();Console.WriteLine("--------------------------------------------");Console.WriteLine("移除订阅者");foreach (User user in userList){Subscriber client = new Subscriber(user.userName);portalPublish.RemoveSubscribe(new NotifySubscribeEventHandler(client.Recevie));}//执行事件 portalPublish.Update();Console.ReadLine();}}}
4、运行结果
