将委托作为中介者/订阅者模式的参数传递

Question

我正在寻找创建带有类型化回调的Mediator/订阅者体系结构的适当而优雅的方法。

假设我有一个带有“events”(即委托)的类：

public class E
{
    public delegate void SomethingHappened (float a, int b);
    public delegate void ProgressFinished (int[] c);
}

现在，我希望创建一个Mediator类，该类将回调注册到这些委托，并使用提供的参数分派回调：

public class Mediator
{
    public static void Register ( ???, Action callback)
    {
        // supplied delegate += callback
    }

    public static void Dispatch ( ???, params object[] list)
    {
        // executing supplied delegate with params: delegate(list)
    }
}

所以我可以用以下方法：

// Class A:
Mediator.Register (E.SomethingHappened, OnSomethingHappened);
private void OnSomethingHappened (float a, int b)
{
    //..........
}

// Class B:
Mediator.Dispatch (E.SomethingHappened, 0.1f, 'qwe');

现在的问题是，我不能将委托作为参数传递给Register。我该如何解决这个问题？

Answer 1

您应该采取一种不同的方法:让您的发件人发送消息，并让您的中介根据它们的类型将它们分派给不同的处理程序。

使用泛型，这将被重构为：

// handlers should be differentiated by message type
public class SomethingHappenedMessage
{
    public float A { get; set; }
    public int B { get; set; }
}

public class Mediator
{
    private readonly Dictionary<Type, object> _dict = new Dictionary<Type, object>();

    public void Register<Tmessage>(Action<Tmessage> callback)
    {
        _dict[typeof(Tmessage)] = callback;
    }

    public void Dispatch<Tmessage>(Tmessage msg)
    {
        var handler = _dict[typeof(Tmessage)] as Action<Tmessage>;
        handler(msg);
    }
}

或者，您可能对每种消息类型都有多个处理程序：

public class Mediator
{
    readonly Dictionary<Type, List<object>> _handlersByType = new Dictionary<Type, List<object>>();

    public void Register<Tmessage>(Action<Tmessage> callback)
    {
        List<object> handlers;
        if (!_handlersByType.TryGetValue(typeof(Tmessage), out handlers))
            _handlersByType[typeof(Tmessage)] = handlers = new List<object>();

        handlers.Add(callback);
    }

    public void Dispatch<Tmessage>(Tmessage msg)
    {
        List<object> handlers;
        if (!_handlersByType.TryGetValue(typeof(Tmessage), out handlers))
            return;

        foreach (Action<Tmessage> handler in handlers)
            handler(msg);
    }
}