PowerShell 中的用户输入验证

Question

我在 PowerShell 中有这段代码。我需要对整数进行用户输入验证，并写入输出说明输入有什么问题并期待正确的输入。

$FromObj = "Please input object number"
$FromInput = Read-Host $FromObj

while(($FromInput -isnot [int])) {
    #I also want to put in the while that the input has to be an integer, -gt 0, and -lt 800
    Write-Output "Your input has to be a number."
    $FromInput = Read-Host $FromObj
    }
if ($FromInput -le 0) {
    Write-Output "Your input has to be a number greater than 0!"
    $FromInput = Read-Host $FromObj
    }
elseif ($FromInput -ge 800) {
    Write-Output "Your input has to be a number less than 800!"
    $FromInput = Read-Host $FromObj
    }
else {
    $FromInput = $FromInput -as [int]
    }

但是，这对我不起作用。你能帮我用上面显示的输出来验证它吗？

Answer 1

我认为Nicks's link in comment 已经为您的问题提供了不同的正确答案，即：使用regex 匹配\d+（数字）或使用[int]::TryParse(...)，但要解释为什么您的代码不起作用：

• Read-Host 会将用户输入存储为 string，除非您在最后一个条件下（else {...} 语句）操作它。

这就是为什么您永远无法通过 $FromInput -isnot [int] 条件的原因。

要修复代码，您可以简单地尝试从一开始就存储用户输入 -as [int]，并且由于您的代码中有 3 个 Read-Host，您可以将用户输入尝试 -as [int] 保存在 ScriptBlock 中，然后可以可以根据需要轻松执行多次：

$FromObj = "Please input object number"
$giveMeNumber = { (Read-Host $FromObj) -as [int] }
$FromInput = & $giveMeNumber

while($FromInput -isnot [int]) {
    Write-Output "Your input has to be a number."
    $FromInput = & $giveMeNumber
}
if ($FromInput -le 0) {
    Write-Output "Your input has to be a number greater than 0!"
    $FromInput = & $giveMeNumber
}
elseif ($FromInput -ge 800) {
    Write-Output "Your input has to be a number less than 800!"
    $FromInput = & $giveMeNumber
}

请注意，即使这样有效，该语句也不完全正确，因为您在输入 is [int] 后打破了 while loop，用户可能会强制输入不正确的输入。

试试这个，它将无限期地执行直到正确的输入：

Clear-Host
$ErrorActionPreference = 'Stop'
$FromObj = "Please input object number"

$scriptBlock = {
    try
    {
        $FromInput = [int](Read-Host $FromObj)

        # Note I'm using Write-Host instead of Write-Ouput, this is because
        # we don't want to store the invalid inputs messages in the
        # $userInput variable.
        if ($FromInput -le 0) {
            Write-Host "Your input has to be a number greater than 0!"
            & $scriptBlock
        }
        elseif ($FromInput -ge 800) {
            Write-Host "Your input has to be a number less than 800!"
            & $scriptBlock
        }
        else {
            $FromInput
        }
    }
    catch
    {
        Write-Host "Your input has to be a number."
        & $scriptBlock
    }
}

$userInput = & $scriptBlock