如何在扩展方法中传递可选参数?

Question

这段代码不起作用，因为我把选项和可选参数弄混了。

如何将选项传递给可选参数?

type Foo() = 
member this.Bar(?name : string, ?number : int) = 
let name = defaultArg name "johndoe"
let number = defaultArg number 0
name + "-" + string number

[<AutoOpen>]
module FooExtensions = 
open System

type Foo with
member this.Bar(?name : string, ?numberAsString : string) = 
let number = 
numberAsString
|> Option.map Int32.Parse
this.Bar(name=name, number=number) // Invalid

Answer 1

您可以在调用方法时将问号前缀放在命名参数上，以表明您希望将值作为option传递。

this.Bar(?name=name, ?number=number)