如何制作一个录音工具的界面? [英] How to make a record implement an interface?

问题描述

如果我有一个界面:

type IData = 
  abstract member firstName: string
  abstract member lastName: string

如何定义符合此接口的记录类型.

How do I define a record type that complies with this interface.

我尝试了以下操作:

> type Data = { firstName: string; lastName: string } interface IData ;;


Snippet.js(43,63): error FS0366: No implementation was given for 'abstract member IData.firstName : string'. Note that all interface members must be implemented
and listed under an appropriate 'interface' declaration, e.g. 'interface ... with member ...'.

从官方参考进行记录:

记录字段与类的不同之处在于它们会自动显示为属性

Record fields differ from classes in that they are automatically exposed as properties

我的第一个问题是:如果属性是自动公开的"，那么为什么我需要做一些事情"来实现它们.

My first question is: If properties are "automatically exposed" then why do I need to "do something" to implement them.

由于错误消息要求我提供该接口的实现，因此我尝试了以下操作:

Since the error message askes me to provide an implementation for the interface, I tried the following:

> type Data = { firstName: string; lastName: string; } interface IData with
-   member this.firstName with get () = this.firstName
-   member this.lastName with get () = this.lastName 

type Data =
  {firstName: string;
   lastName: string;}
  with
    interface IData
  end 

到目前为止还不错，但是现在当我尝试使用它时，我遇到了问题:

So far so good, however now when I try to use this, I run into issues:

> let d: IData = { firstName = "john"; lastName = "doe" } ;;

error FS0001: This expression was expected to have type
    'IData'
but here has type
    'Data'

另一种尝试:

> let d = { firstName = "john"; lastName = "doe" }
- ;;
val d : Data = {firstName = "john";
                lastName = "doe";}

> let d2: IData = d ;;


C:\Users\loref\Workspace\source-nly10r\Untitled-1(25,17): error FS0001: This expression was expected to have type
    'IData'
but here has type
    'Data'

所以，我的第二个问题是，如果Data实现IData，那么为什么不能将Data类型的值分配给IData类型的变量呢?

So, my second question is that if Data implements IData then why can't I assign a value of Data type to a variable of IData type ?

推荐答案

如 Gustavo 所指出的，隐式接口实现是F#实现者正在进行讨论，目前尚不可用.

As pointed by Gustavo, implicit interface implementation is being discussed by F# implementers, and is not currently available.

Wrt.我的第二个问题，需要显式强制转换:

Wrt. my second question, explicit casting is required:

> let d2: IData = d :> IData ;;
val d2 : IData = {firstName = "john";
                  lastName = "doe";}

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