该表达式的类型应为"unit"，但类型应为"ConsoleKeyInfo" [英] This expression should have type 'unit', but has type 'ConsoleKeyInfo'

问题描述

我只是想在F#控制台应用程序中暂停，所以我写道:

I just wanted to pause in an F# console application, so I wrote:

Console.ReadKey()

Console.ReadKey()

但这会发出警告:This expression should have type 'unit', but has type 'ConsoleKeyInfo'.

该如何解决?

推荐答案

解决方案:

Console.ReadKey() |> ignore

说明:Console.ReadKey()返回类型为'ConsoleKeyInfo'的对象，但是您将其用作语句，而没有将返回值分配给任何对象.因此，F#警告您忽略了一个值. ignore采用任何类型，不返回任何内容.可以这样定义:

Explanation: Console.ReadKey() returns an object of type 'ConsoleKeyInfo' but you're using it as a statement without assigning the return value to anything. So F# warns you that you're ignoring a value. ignore takes any type and returns nothing. It could be defined like this:

let ignore _ = ()

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