f# - 一行中的让和属性分配

Question

如何在一行中编写以下 F# 代码（或类似代码）：

let contextMenu = new ContextMenuStrip()
mainForm.ContextMenuStrip <- contextMenu

我必须声明contextMenu，因为稍后将需要它。

Answer 1

You can set public, writeable properties as pseudo-parameters in the constructor.

let contextMenu = new ContextMenuStrip()
let form = new Form(ContextMenuStrip = contextMenu)

Answer 2

我不建议您将其写在一行上，因为这意味着它将是#light（现在默认的模式）和非#light 语法之间的混合。如果你真的需要，你可以使用 ;; 像那样：

open System
open System.Windows.Forms

let mainForm = new Form()
let contextMenu = new ContextMenuStrip();; mainForm.ContextMenuStrip <- contextMenu;;

如果您的表达式具有单元类型，您可以使用顺序执行表达式，它是以下形式的表达式：

expr1; expr2; expr3

例如：

mainForm.ContextMenuStrip <- contextMenu; 5 + 6 |> ignore; mainForm.ContextMenuStrip <- null

我想补充一点，顺序执行表达式与非 #light 模式无关。它们只是一种通用的语言结构。

希望能帮助到你。

Answer 3

You could also type

let contextMenu = new ContextMenuStrip() in mainForm.ContextMenuStrip <- contextMenu

This is OCaml syntax, IIRC.

Edit: to be more clear: this is also valid (#light) F# syntax, since F# is based on OCaml.

I also don't recommend doing this, even though I like short programs.