Question

我有一个玩具问题，感觉应该很简单。我想拥有一个支持管道的Join-Path等功能。称之为Build-Path。因此，这些陈述（我的测试1-4）应该是等同的：

Get-Location | Build-Path Test

Get-Location | Build-Path -Right Test

Build-Path -Left (Get-Location) -Right Test

Build-Path (Get-Location) Test

我已经尝试了很多东西，最接近我可以获得这两个功能（互斥）：

A：两个值的显式位置;未通过测试1

function Build-Path
(
    [Parameter(Mandatory=$true, Position=0, ValueFromPipeline=$true)]
    [String] $Left, 
    [Parameter(Mandatory=$true, Position=1)]
    [String] $Right
)
{
    Join-Path $Left $Right
}

B：管道参数没有位置，Right的位置为0;未通过测试4

function Build-Path
(
    [Parameter(Mandatory=$true, ValueFromPipeline=$true)]
    [String] $Left, 
    [Parameter(Mandatory=$true, Position=0)]
    [String] $Right
)
{
    Join-Path $Left $Right
}

我尝试过多种方式使用ParameterSets（没有保存我的尝试）但没有成功，我现在有点难过。

思想？

Answer 1

这不能按你想要的方式工作。你的两个参数都是相同的数据类型，PowerShell会在查看它是否进入管道之前使用它来绑定参数，并且它会尝试立即从0开始填充位置。

我甚至尝试使用参数集重做它：

function Build-Path {
[CmdletBinding(DefaultParameterSetName='Default',PositionalBinding=$false)]
param(
    [Parameter(
        ParameterSetName='Default',
        Mandatory=$true, 
        ValueFromPipeline=$true
    )]
    [Parameter(
        ParameterSetName='LooseyGoosey',
        Mandatory=$true,
        Position=0
    )]
    [String] 
    $Left, 

    [Parameter(
        ParameterSetName='Default',
        Mandatory=$true, 
        Position=0
    )]
    [Parameter(
        ParameterSetName='LooseyGoosey',
        Mandatory=$true,
        Position=1
    )]
    [String] 
    $Right
)

    Join-Path $Left $Right
}

要了解PowerShell如何绑定参数，请使用Trace-Command：

Trace-Command -Name ParameterBinding -Expression { Build-Path (Get-Location) Test } -Verbose -PSHost

无论你如何切片，你都会遇到问题。没有DefaultParameterSet？参数集无法解析。切换默认值？然后你只是改变哪些调用工作或不工作。

您也无法将-Right参数设为[String[]]数组，因为在绑定期间PowerShell会尝试强制执行，因此[String]仍将被接受并绑定。

DEBUG: ParameterBinding Information: 0 : BIND NAMED cmd line args [Get-Location]
DEBUG: ParameterBinding Information: 0 : BIND POSITIONAL cmd line args [Get-Location]
DEBUG: ParameterBinding Information: 0 : BIND cmd line args to DYNAMIC parameters.
DEBUG: ParameterBinding Information: 0 : MANDATORY PARAMETER CHECK on cmdlet [Get-Location]
DEBUG: ParameterBinding Information: 0 : CALLING BeginProcessing
DEBUG: ParameterBinding Information: 0 : CALLING EndProcessing
DEBUG: ParameterBinding Information: 0 : BIND NAMED cmd line args [Build-Path]
DEBUG: ParameterBinding Information: 0 : BIND POSITIONAL cmd line args [Build-Path]
DEBUG: ParameterBinding Information: 0 :     BIND arg [C:\Users\Briantist] to parameter [Right]
DEBUG: ParameterBinding Information: 0 :         Executing DATA GENERATION metadata: [System.Management.Automation.ArgumentTypeConverterAttribute]
DEBUG: ParameterBinding Information: 0 :             result returned from DATA GENERATION: C:\Users\Briantist
DEBUG: ParameterBinding Information: 0 :         BIND arg [C:\Users\Briantist] to param [Right] SKIPPED
DEBUG: ParameterBinding Information: 0 :     BIND arg [C:\Users\Briantist] to parameter [Left]
DEBUG: ParameterBinding Information: 0 :         Executing DATA GENERATION metadata: [System.Management.Automation.ArgumentTypeConverterAttribute]
DEBUG: ParameterBinding Information: 0 :             result returned from DATA GENERATION: C:\Users\Briantist
DEBUG: ParameterBinding Information: 0 :         BIND arg [C:\Users\Briantist] to param [Left] SKIPPED
DEBUG: ParameterBinding Information: 0 :     BIND arg [C:\Users\Briantist] to parameter [Right]
DEBUG: ParameterBinding Information: 0 :         Executing DATA GENERATION metadata: [System.Management.Automation.ArgumentTypeConverterAttribute]
DEBUG: ParameterBinding Information: 0 :             result returned from DATA GENERATION: C:\Users\Briantist
DEBUG: ParameterBinding Information: 0 :         BIND arg [C:\Users\Briantist] to param [Right] SKIPPED
DEBUG: ParameterBinding Information: 0 :     BIND arg [C:\Users\Briantist] to parameter [Right]
DEBUG: ParameterBinding Information: 0 :         Executing DATA GENERATION metadata: [System.Management.Automation.ArgumentTypeConverterAttribute]
DEBUG: ParameterBinding Information: 0 :             result returned from DATA GENERATION: C:\Users\Briantist
DEBUG: ParameterBinding Information: 0 :         COERCE arg to [System.String]
DEBUG: ParameterBinding Information: 0 :             Parameter and arg types the same, no coercion is needed.
DEBUG: ParameterBinding Information: 0 :         BIND arg [C:\Users\Briantist] to param [Right] SUCCESSFUL
DEBUG: ParameterBinding Information: 0 :     BIND arg [Test] to parameter [Right]
DEBUG: ParameterBinding Information: 0 :         Executing DATA GENERATION metadata: [System.Management.Automation.ArgumentTypeConverterAttribute]
DEBUG: ParameterBinding Information: 0 :             result returned from DATA GENERATION: Test
DEBUG: ParameterBinding Information: 0 :         BIND arg [Test] to param [Right] SUCCESSFUL
DEBUG: ParameterBinding Information: 0 : MANDATORY PARAMETER CHECK on cmdlet [Build-Path]
DEBUG: ParameterBinding Information: 0 :     PROMPTING for missing mandatory parameters using the host

PowerShell：位置参数和ValueFromPipeline

1 个答案: