在F#中实现ThreadStatic单例

Question

我正在学习F#并希望实现ThreadStatic单例.我正在使用我在类似问题中找到的内容:F#如何实现Singleton Pattern(语法)

使用以下代码编译器抱怨The type 'MySingleton' does not have 'null' as a proper value.

type MySingleton = 
    private new () = {}
    [<ThreadStatic>] [<DefaultValue>] static val mutable private instance:MySingleton
    static member Instance =
        match MySingleton.instance with
        | null -> MySingleton.instance <- new MySingleton()
        | _ -> ()
        MySingleton.instance

我如何在这种情况下初始化实例？

Answer 1

我认为[<ThreadStatic>]导致相当笨重的代码,特别是在F#中.有更简洁的方法可以做到这一点,例如,使用ThreadLocal:

open System.Threading

type MySingleton private () = 
  static let instance = new ThreadLocal<_>(fun () -> MySingleton())
  static member Instance = instance.Value