F# 向上转换基础

Question

当我想将 base 向上转换为适当的接口(interface)类型(即 A)以便我可以在其上调用 doA() 时，我遇到了一个解析错误。我知道 base ( http://cs.hubfs.net/topic/None/58670 ) 有些特殊，但到目前为止我还没有找到解决这个特定问题的方法。

有什么建议吗？

type A =
    abstract member doA : unit -> string

type ConcreteA() =
    interface A with
        member this.doA() = "a"

type ExtA() = 
    inherit ConcreteA()


interface A with
    override this.doA() = "ex" // + (base :> A).doA() -> parse error (unexpected symbol ':>' in expression)

((new ExtA()) :> A).doA() // output: ex

工作的 C# 等价物:

public interface A
{
    string doA();
}

public class ConcreteA : A {
    public virtual string doA() { return "a"; }
}

public class ExtA : ConcreteA {
    public override string doA() { return "ex" + base.doA(); }
}

new ExtA().doA(); // output: exa

Answer 1

这相当于您的 C#:

type A =
    abstract member doA : unit -> string

type ConcreteA() =
    abstract doA : unit -> string
    default this.doA() = "a"
    interface A with
        member this.doA() = this.doA()

type ExtA() = 
    inherit ConcreteA()
    override this.doA() = "ex" + base.doA()

ExtA().doA() // output: exa

base 不能单独使用，只能用于成员访问(因此会出现解析错误)。请参阅 Classes on MSDN 下的指定继承 .