C#等同于Java的List&lt ;?扩展MyFancyClass> [英] C# equivalent of Java's List<? extends MyFancyClass>

问题描述

我不相信我在任何地方都看到了这一点(我不确定该如何真正表达这个问题，所以可能是为什么)，所以，如果已经回答了，我表示歉意.

I don't believe I saw this anywhere (I'm not sure how to word the question really so that may be why) so if it's already been answered I apologise.

我目前正在编写一个具有事件API的应用程序，第三方可以将其插入其中，以下是我用来触发事件的代码.

I'm currently writing an application that has an event API that third parties can hook into, below is the code I'm using to fire the events.

// Events.cs from the API project
public interface IEventListener
{
    void Handle(IEvent @event);
}

public abstract class EventManager
{
    public abstract void Register(PluginBase plugin, IEventListener listener);
    public abstract void Call(IEvent @event);
}

// Events.cs from the main project
public class SimpleEventManager : EventManager
{
    private readonly Dictionary<PluginBase, List<IEventListener>> _events = 
        new Dictionary<PluginBase, List<IEventListener>>();

    public override void Register(PluginBase plugin, IEventListener listener)
    {

    }

    public override void Call(IEvent @event)
    {
       // Iterate through _events.Values and call Handle on each IEventListener
    }
}

虽然上面的代码可以正常工作，但我发现第三方如何将其钩到非常丑陋的位置，并且想知道是否有可能使用 Action 类将其连接起来.

Whilst the code above works fine I find how third parties hook into it to be incredibly ugly and was wondering if it would be possible to hook it up to use the Action class.

// TestPlugin.cs
class MyTestPlugin : PluginBase
{
    var handler = new MyEventHandler();
    App.Instance.EventManager.Register(this, handler);
}

class MyEventHandler : IEventListener
{
   public void Handle(IEvent @event)
   {
       if(@event is SomeEvent) HandleSomeEvent((SomeEvent) @event);
   }

   private void HandleSomeEvent(SomeEvent someEvent)
   {
       // Handle the event of course
   }
}

我的目标是将Register方法更改为接受第三个参数 Action< IEvent> ，尽管我发现如果我引用一个方法，则它必须严格接受IEvent作为参数.在Java中，您可以使用< ;?扩展BaseClass> (自我解释)，是否有类似 Action<的东西?:IEvent> 还是根本不可能?

My goal is to change the Register method to accept a third parameter, Action<IEvent> though I've found out that if I reference a method then it must strictly accept an IEvent as an argument. In Java you can use <? extends BaseClass> (self explanatory), is there something like Action<? : IEvent> or is this simply not possible?

推荐答案

此功能称为通用约束".您可以这样表达:

This feature is called "generic constraints". You'd express it like this:

public interface IEventListener<TEvent> where TEvent: IEvent
{
    void Handle(TEvent @event);
}

class MyEventHandler : IEventListener<SomeEvent>
{
   public void Handle(SomeEvent @event)
   {
       // Handle the event of course
   }
}

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