设计模式之-中介者模式
中介者模式是一个行为设计模式，它允许我们公开一个统一的接口，系统的 不同部分 可以通过该接口进行 通信，而 不需要 显示的相互作用；
主要解决：对象与对象之间存在大量的关联关系，这样势必会导致系统的结构变得很复杂，同时若一个对象发生改变，我们也需要跟踪与之相关联的对象，同时做出相应的处理。
关键：各个原本关联的对象不在互相关联，而是由中介者掌握他们关联的信息。类似我们在找中介租房，我们并不知道房东是谁，房东也不知道我们是谁，因为房东把房子的信息交给了中介。因此，在中介者模式中，只需要让中介者知道如何关联即可。
以下例子是我的理解，或许有不正确的地方。
class Program { static void Main(string[] args) { var register = new Dictionary<Person, Person>(); IMediator mediator = new Mediator(register); var student = new Student(mediator,"萌新","学生"); var teacher = new Teacher(mediator, "大佬", "老师"); register.Add(student, teacher); register.Add(teacher, student); student.Send("老师你好"); teacher.Send("你好同学"); Console.ReadKey(); } } public abstract class Person { /// <summary> /// 构造函数。 /// </summary> /// <param name="name">名字。</param> /// <param name="identity">身份。</param> protected Person(string name, string identity) { this.Name = name; this.Identity = identity; } /// <summary> /// 名字。 /// </summary> public string Name { get; } /// <summary> /// 身份。 /// </summary> public string Identity { get; } /// <summary> /// 发送信息。 /// </summary> /// <param name="msg">信息。</param> public abstract void Send(string msg); /// <summary> /// 接收信息。 /// </summary> /// <param name="msg">信息。</param> public abstract void Receive(string msg); } /// <summary> /// 中介者接口。 /// </summary> public interface IMediator { /// <summary> /// 转发信息。 /// </summary> /// <param name="msg">信息。</param> /// <param name="person">信息发起人。</param> void Transmit(string msg, Person person); } /// <summary> /// 实现类。 /// </summary> public class Mediator : IMediator { /// <summary> /// 信息发起人对信息接收人。 /// </summary> private readonly Dictionary<Person, Person> _register; /// <summary> /// 由中介者管理关系。 /// </summary> /// <param name="register"></param> public Mediator(Dictionary<Person, Person> register) { _register = register; } /// <summary> /// 中介者调用关系。 /// </summary> /// <param name="msg">信息。</param> /// <param name="person">发信息的人。</param> public void Transmit(string msg, Person person) { var pr = _register[person]; pr.Receive(msg); } } public class Student : Person { /// <summary> /// 中介者接口。 /// </summary> private readonly IMediator _mediator; /// <summary> /// 构造函数。 /// </summary> /// <param name="mediator">中介者。</param> /// <param name="name">名字。</param> /// <param name="identity">身份。</param> public Student(IMediator mediator, string name, string identity) : base(name, identity) { _mediator = mediator; } /// <summary> /// 接收信息。 /// </summary> /// <param name="msg">信息。</param> public override void Receive(string msg) { Console.WriteLine($"{Identity}-{Name}:收到信息:{msg}"); } /// <summary> /// 发送信息。 /// </summary> /// <param name="msg">信息。</param> public override void Send(string msg) { _mediator.Transmit(msg, this); } } public class Teacher : Person { private readonly IMediator _mediator; public Teacher(IMediator mediator, string name, string identity) : base(name, identity) { _mediator = mediator; } public override void Receive(string msg) { Console.WriteLine($"{Identity}-{Name}:收到信息:{msg}"); } public override void Send(string msg) { _mediator.Transmit(msg, this); } }
由nuget包：MediatR的请求响应模式的中介者。
class Program { static void Main(string[] args) { var register = new Dictionary<Person, Person>(); var student = new Student("萌新", "学生"); var teacher = new Teacher("大佬", "老师"); register.Add(student, teacher); register.Add(teacher, student); var service = new ServiceCollection(); service.AddMediatR(typeof(Program)); service.AddScoped<IMediatorHandler, MediatorHandler>(); service.AddScoped<SenPersonHandler>(); service.AddSingleton(register); service.AddScoped<IRequestHandler<Student, bool>, SenPersonHandler>(); service.AddScoped<IRequestHandler<Teacher, bool>, SenPersonHandler>(); var provide = service.BuildServiceProvider(); var medi = provide.GetService<IMediatorHandler>(); student.Send("老师你好"); medi.SendRequest(student); teacher.Send("你好同学"); medi.SendRequest(teacher); Console.ReadKey(); } } /// <summary> /// 由MediatR需要的实现关联。 /// </summary> public class SenPersonHandler : IRequestHandler<Student, bool>, IRequestHandler<Teacher, bool> { private readonly Dictionary<Person, Person> _register; public SenPersonHandler(Dictionary<Person, Person> register) { _register = register; } public Task<bool> Handle(Student request, CancellationToken cancellationToken) { var pr = _register[request]; pr.Receive(request.Msg); return Task.FromResult(true); } public Task<bool> Handle(Teacher request, CancellationToken cancellationToken) { var pr = _register[request]; pr.Receive(request.Msg); return Task.FromResult(true); } } /// <summary> /// 人。 /// </summary> public abstract class Person : IRequest<bool> { /// <summary> /// 信息。 /// </summary> public string Msg { get; protected set; } /// <summary> /// 必须要性名和身份。 /// </summary> /// <param name="name">名字。</param> /// <param name="identity">身份。</param> protected Person(string name, string identity) { Name = name; Identity = identity; } /// <summary> /// 名字。 /// </summary> public string Name { get; } /// <summary> /// 身份信息。 /// </summary> public string Identity { get; } /// <summary> /// 发送。 /// </summary> /// <param name="msg">发送信息。</param> public abstract void Send(string msg); /// <summary> /// 接收信息。 /// </summary> /// <param name="msg">信息。</param> public abstract void Receive(string msg); } /// <summary> /// 中介者接口。 /// </summary> public interface IMediatorHandler { /// <summary> /// 发送请求。 /// </summary> /// <typeparam name="T">类型。</typeparam> /// <param name="request">请求。</param> /// <returns></returns> Task SendRequest<T>(T request) where T : Person; } /// <summary> /// 中介者实现类。 /// </summary> public class MediatorHandler : IMediatorHandler { /// <summary> /// 内置IMediator。 /// </summary> private readonly IMediator _mediator; public MediatorHandler(IMediator mediator) { _mediator = mediator; } /// <summary> /// 发送请求。 /// </summary> /// <typeparam name="T">Person类型。</typeparam> /// <param name="request">请求者。</param> /// <returns></returns> public Task SendRequest<T>(T request) where T : Person { _mediator.Send(request); return Task.CompletedTask; } } public class Student : Person { public Student(string name, string identity) : base(name, identity) { } public override void Receive(string msg) { Console.WriteLine($"{Identity}-{Name}:收到信息:{msg}"); } public override void Send(string msg) { Msg = msg; } } public class Teacher : Person { public Teacher(string name, string identity) : base(name, identity) { } public override void Receive(string msg) { Console.WriteLine($"{Identity}-{Name}:收到信息:{msg}"); } public override void Send(string msg) { Msg = msg; } }