给定一个受成员约束约束的值,我可以作为一等函数访问该成员吗？

Question

是否可以将受约束的成员作为第一类函数(给定对象)进行访问？如果是这样,使用的语法是什么？

  // Example: property getter as a first-class function
  type Test() =
     member x.Value = "42"

  let t = Test()
  let getter = t.get_Value // works as expected


  // now generically:
  let inline getGetter< ^a when ^a : (member get_Value : unit -> string)> item =
    // call getter
    let value = (^a : (member get_Value : unit -> string) item)
    // try to get getter as first-class function
    let getter = item.get_Value // doesn't compile: "Lookup on object of indeterminate type..."
    ()

Answer 1

我认为这就是你要找的东西:

  type Test() =
     member x.Value = "42"

  let inline getGetter< ^a when ^a : (member get_Value : unit -> string)> item =
    fun () -> (^a : (member get_Value : unit -> string) item)

  let t = Test()
  let getter = getGetter t
  let value = getter()