以通用类型引用当前对象的关键字 [英] A keyword to reference the current object as a generic type

问题描述

我有一个简单的泛型委托人:

I have a simple generic delegate:

delegate void CommandFinishedCallback<TCommand>(TCommand command) 
    where TCommand : CommandBase;

我在以下抽象类中使用它:

I use it in the following abstract class:

public abstract class CommandBase
{
    public CommandBase()
    { }

    public void ExecuteAsync<TCommand>(CommandFinishedCallback<TCommand> callback)
        where TCommand : CommandBase
    {
        // Async stuff happens here

        callback.Invoke(this as TCommand);
    }
}

这确实可行，但我无法强制将传递给Execute的TCommand设置为当前对象的类型(派生自更多的CommandBase).

While this does work, I have no way of forcing the TCommand passed into Execute to be the type of the current object (the more derived CommandBase).

我看到这样做可以解决此问题:

I've seen this solved by doing:

public abstract class CommandBase<TCommand>
    where TCommand : CommandBase<TCommand>
{ 
    // class goes here
}

但是我想知道为什么没有C#关键字来实现这一目标?我很想看的是以下内容:

But I'm wondering why there isn't a C# keyword for accomplishing that? What I'd love to see is something like the following:

public void ExecuteAsync<TCommand>(CommandFinishedCallback<TCommand> callback)
    where TCommand : This
{
    // Async stuff happens here

    callback.Invoke(this);
}

注意"This"上的大写字母T.我绝不是语言设计师，但我很好奇我是否要去吃午餐.这会是CLR可以处理的吗?

Note the capital T on "This". I'm by no means a language designer, but I'm curious if I'm out to lunch or not. Would this be something the CLR could handle?

也许已经有解决问题的模式了?

Maybe there's already a pattern for solving the problem?

推荐答案

不，没有 thistype 约束.埃里克·利珀特(Eric Lippert)在这里对此有一些沉思:

No, there is no thistype constraint. There are some musings on this topic by Eric Lippert here: Curiouser and curiouser.

请特别注意， CRTP (问题的解决方案")是'这实际上是一个解决方案.

Note, in particular, the CRTP (your "solution" to the problem) isn't actually a solution.

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