inheritance - f# 类型提供程序继承

Question

我设计了一个简单的类型提供程序，它根据我的参数提供类型。我想知道是否可以定义会继承另一个 ProvidedTypeDefinition 的 ProvidedTypeDefinition？

我知道静态我可以执行以下操作:

type People() = class end

type Student() =
    inherit People() 

type Teacher() =
    inherit People()

然后我可以使用类型测试模式进行模式匹配:

let f (x:People) =
    match x with
        | :? Student -> "Student"
        | :? Teacher -> "Teacher"
        | _ -> "Nothing !!"

我想在我的类型提供程序中做的是创建继承另一个 ProvidedTypeDefinition 的 ProvidedTypeDefinition。这样，当我使用类型提供程序生成这些类型时，我可以对它们进行模式匹配(例如，我知道在运行时将实例化这种类型之一，但我不知道是哪一个，除了它是 ProvidedTypeDefinitions 之一)。

感谢您的时间!

Answer 1

尝试使用 Discriminated Union 进行模式匹配而不是继承

type Occupation =
  | Student
  | Teacher

type People(occupation) = 
  member this.Occupation = occupation
class end

type Student() =
  inherit People(Student) 

type Teacher() =
  inherit People(Teacher)

let findPerson (person : People) =
  match person.Occupation with
    | Student -> "Student"
    | Teacher -> "Teacher"

我个人喜欢避免在 fsharp 中使用对象继承，因为 upcasting and downcasting .例如，

let person = new Student() :> People
findPerson person

相反，我建议摆脱学生和老师的解析，让人们处理职业逻辑。

type Occupation =
  | Student
  | Teacher

type People(occupation) = 
  member this.Occupation = occupation
class end

let findPerson (person : People) =
  match person.Occupation with
    | Student -> "Student"
    | Teacher -> "Teacher"

People Student
|> findPerson
|> printfn "%s"