将PowerShell数组传递给函数时如何扩展它

Question

我有两个 PowerShell 函数，第一个调用第二个。它们都采用 N 个参数，其中一个被定义为简单地添加一个标志并调用另一个。以下是示例定义：

function inner
{
  foreach( $arg in $args )
    {
      # do some stuff
    }
}

function outer
{
  inner --flag $args
}

用法如下所示：

inner foo bar baz

或者这个

outer wibble wobble wubble

目标是使后一个示例等效于

inner --flag wibble wobble wubble

问题：正如这里定义的那样，后者实际上导致两个参数被传递给inner：第一个是“--flag”，第二个是包含“wibble”的数组、“摇摆”和“摇摆”。我想要的是inner 接收四个参数：标志和三个原始参数。

所以我想知道的是如何说服 powershell 在将 $args 数组传递给inner 之前扩展它，将它作为 N 个元素而不是单个数组传递。我相信你可以在 Ruby 中使用 splatting 运算符（* 字符）做到这一点，我很确定 PowerShell 可以做到，但我不记得是如何做到的。

Answer 1

PowerSHell V1 中没有很好的解决方案。在 V2 中，我们添加了 splatting（尽管出于各种原因，我们为此使用 @ 而不是 *）。这是它的样子：

PS (STA-ISS) (2) > 函数 foo ($x,$y,$z) { "x:$x y:$y z:$z" }

PS (STA-ISS) (3) > $a = 1,2,3

PS (STA-ISS) (4) > foo $a # 作为单个 arg 传递

x:1 2 3 y:z:

PS (STA-ISS) (5) > foo @a # splatted

x:1 y:2 z:3

Answer 2

嗯，可能有更好的方法，但看看这是否可行：

inner --flag [string]::Join(" ", $args)

Answer 3

基于@EBGreen 的想法，以及我在侧边栏中注意到的一个相关问题，一个可能的解决方案是：

function outer
{
    invoke-expression "inner --flag $($args -join ' ')"
}

注意：此示例使用 Powershell 2.0 CTP 的新 -join 运算符。

但是，我仍然想找到一种更好的方法，因为这感觉像是一种黑客攻击，并且在安全方面非常糟糕。

Answer 4

如果你想要一个快速的现成解决方案，你可以复制粘贴我的：

<#
    .SYNOPSIS
    Asks a question and waits for user's answer

    .EXAMPLE
    Usage with shortcuts and without ReturnValue
    Invoke-Question -Question "What would you like" -Answers "&Eggs", "&Toasts", "&Steak"

    Shows the quesiton and waits for input. Let's assume user input is 'S', the return value would be 2 (index of "&Steak")

    .EXAMPLE
    Usage without shortcuts and with ReturnValue
    Invoke-Question -Question "What would you like" -Answers "Eggs", "Toasts", "Steak" -ReturnValue

    Shows the quesiton and waits for input. The answers are prefixed with numbers 1, 2 and 3 as shortcuts.
    Let's assume user input is 2, the return value would be "Toasts" (prefixed numbers are "index + 1")

    .EXAMPLE
    Usage from pipeline with default value
    @("Eggs", "Toasts", "Steak") | Invoke-Question -Question "What would you like" -ReturnValue -Default 2

    Shows the quesiton and waits for input. The answers are taken from pipeline and prefixed with numbers 1, 2 and 3 as shortcuts.
    Steak is marked as default. If user simply continues without a choice, Steak is chosen for her.
    However, let's assume user input is 1, the return value would be "Eggs" (prefixed numbers are "index + 1")
#>
function Invoke-Question {
    [CmdletBinding()]
    param(
        # Main question text
        [Parameter(Mandatory = $true)]
        [string] $Question,

        # Question description, e.g. explanation or more information
        [Parameter(Mandatory = $false)]
        [string] $Description = "",

        # Default answer as index in the array, no answer is selected by default (value -1)
        [Parameter(Mandatory = $false)]
        [int] $Default = -1,

        # Set of answers, if the label is given with & sign, the prefixed letter is used as shortcut, e.g. "&Yes" -> Y,
        # otherwise the answer is prefixed with "index + 1" number as a shortcut
        [Parameter(Mandatory = $true, ValueFromPipeline = $true)]
        [string[]] $Answers,

        # If set, returns a value of selected answer, otherwise returns its index in the Answer array
        [switch] $ReturnValue
    )

    begin {
        # init choices
        $choices = New-Object Collections.ObjectModel.Collection[Management.Automation.Host.ChoiceDescription]
        $answerNumber = 1
        $rememberAnswers = @()
    }

    process {
        #init answers
        foreach ($answer in $answers) {
            $rememberAnswers += $answer
            if ($answer -notmatch "&") {
                # add number if shortcut not specified
                $answer = "&$answerNumber $answer"
            }

            $choices.Add((New-Object Management.Automation.Host.ChoiceDescription -ArgumentList $answer))
            $answerNumber++
        }
    }

    end {
        # ask question and return either value or index
        $index = $Host.UI.PromptForChoice($Question, $Description, $choices, $Default)
        if ($ReturnValue) {
            $rememberAnswers[$index]
        } else {
            $index
        }
    }
}