F# | шаблон Value Object

type UserName = private | UserName of string

module UserName =
    let isValid s =
        System.String.IsNullOrWhiteSpace(s) |> not

    let create (str: string) =
        if isValid str then Some(UserName str) else None

    let value (UserName s) = s

(* Применение *)

match (UserName.create "Alice") with
| Some name -> name |> UserName.value
| None -> "empty"