问题
I just wanted to pause in an F# console application, so I wrote:
Console.ReadKey()
But this gives the warning: This expression should have type 'unit', but has type 'ConsoleKeyInfo'.
What can I do to fix this?
回答1:
Solution:
Console.ReadKey() |> ignore
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 _ = ()
来源:https://stackoverflow.com/questions/324947/this-expression-should-have-type-unit-but-has-type-consolekeyinfo