在 F# 中，如何实现具有父接口和祖父接口的接口？

Question

当继承多个接口时，在 F# 中实现它们的正确方法是什么？

例如，假定以下接口层次结构，ITranscript 在 TranscriptNote 类型上的实现给出：

“值或构造函数'tservice'未定义。”

type TranscriptNote =
   {      
        tservice : Nullable<DateTime>      
   }
   interface ITranscript with 
       member this.tservice with get() = tservice and set value = tservice <- value 

"The value or constructor 'tservice' is not defined."

where ITranscript is :

type ITranscript =
    inherit ITablet
    abstract member note : byte[] with get
    abstract member transcript: string with get

type ITablet = 
    inherit IParagraph
    inherit IInk

type IParagraph = 
    inherit IEncounter
    abstract member paragraphTitle : string with get
    abstract member title : string with get

type IEncounter = 
    abstract member tservice : Nullable<DateTime> with get,set

提前感谢您的帮助。

Answer 1

更新：@JL0PD 对您看到的编译器错误有正确的解释。我已经从我的答案中删除了不正确的信息，但保留了其余信息。

一种方法是分别实现每个接口。在每个接口下，仅实现该接口明确定义的成员：

type IGrandparent =
    abstract member GetName : unit -> string

type IParent =
    inherit IGrandparent
    abstract member GetCount : unit -> int

type MyType() =
    interface IGrandparent with
        member __.GetName() = "name"
    interface IParent with
        member __.GetCount() = 1

let obj = MyType() :> IParent
printfn "%A" <| obj.GetName()
printfn "%A" <| obj.GetCount()

请注意，我没有在 IParent 下实现 GetName，但由于继承，我仍然可以在 IParent 实例上调用 GetName。

Answer 2

如果你想用原始结构编译它，你的类型应该是这样的。但即使 F# 支持 OOP，也并不意味着那总是最好的方式，阅读 style guide P 3 & 4. F# is not C# with different syntax, it's different language with different core principles. Maybe your hierarchy can be represented better with DU

// [<CLIMutable>] // uncomment this line to make all fields mutable
type TranscriptNote =
    {
        // instances can be mutated, but only this field
        mutable tservice : Nullable<DateTime>
    }
    interface ITranscript with
        // stubs
        member _.note = [| |] // empty array
        member _.paragraphTitle = "some title"
        member _.title = "some another title"
        member _.transcript = "some transcript"

        member this.tservice with get() = this.tservice // need 'this' to get access to field
                             and set value = this.tservice <- value

注意：您不必单独实现每个接口，但它可能有助于维护。

在 F# 中，如何实现具有父接口和祖父接口的接口？

In F#, how to implement an interface with parent and grandparent interfaces?

inheritance

f#

interface