powershell - PS 流水线多参数绑定(bind)

Question

我试图通过管道将两个参数传递给一个函数，但它似乎没有按预期工作，我很难理解为什么。

MWE

function Test-Pipeline {
  [CmdletBinding ()]
  Param(
    [Parameter(ValueFromPipeline=$true)][String]$Name,
    [Parameter(ValueFromPipeline=$true)][String]$Value
  )
  Write-Host "Name: $Name"
  Write-Host "Value: $Value"
}

"Name", "Value" | Test-Pipeline

输出

Name: Value

Value: Value

我尝试运行 Trace-Command 命令来查看发生了什么。在第 35 行，我们可以看到 Value 绑定(bind)到 $Parameter。

为什么 PowerShell 将第二个输入绑定(bind)到两个参数？如果这是预料之中的，为什么它只出现在第二个参数而不出现在第一个参数上？

跟踪

DEBUG: ParameterBinding Information: 0 : BIND NAMED cmd line args [Test-Pipeline]
DEBUG: ParameterBinding Information: 0 : BIND POSITIONAL cmd line args [Test-Pipeline]
DEBUG: ParameterBinding Information: 0 : MANDATORY PARAMETER CHECK on cmdlet [Test-Pipeline]
DEBUG: ParameterBinding Information: 0 :     BIND arg [] to parameter [Name]
DEBUG: ParameterBinding Information: 0 :         Executing DATA GENERATION metadata: [System.Management.Automation.ArgumentTypeConverterAttribute]
DEBUG: ParameterBinding Information: 0 :             result returned from DATA GENERATION:
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 [] to param [Name] SUCCESSFUL
DEBUG: ParameterBinding Information: 0 :     BIND arg [] to parameter [Value]
DEBUG: ParameterBinding Information: 0 :         Executing DATA GENERATION metadata: [System.Management.Automation.ArgumentTypeConverterAttribute]
DEBUG: ParameterBinding Information: 0 :             result returned from DATA GENERATION:
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 [] to param [Value] SUCCESSFUL
DEBUG: ParameterBinding Information: 0 : CALLING BeginProcessing
DEBUG: ParameterBinding Information: 0 : BIND PIPELINE object to parameters: [Test-Pipeline]
DEBUG: ParameterBinding Information: 0 :     PIPELINE object TYPE = [System.String]
DEBUG: ParameterBinding Information: 0 :     RESTORING pipeline parameter's original values
DEBUG: ParameterBinding Information: 0 :     Parameter [Value] PIPELINE INPUT ValueFromPipeline NO COERCION
DEBUG: ParameterBinding Information: 0 :     BIND arg [Name] to parameter [Value]
DEBUG: ParameterBinding Information: 0 :         Executing DATA GENERATION metadata: [System.Management.Automation.ArgumentTypeConverterAttribute]
DEBUG: ParameterBinding Information: 0 :             result returned from DATA GENERATION: Name
DEBUG: ParameterBinding Information: 0 :         BIND arg [Name] to param [Value] SUCCESSFUL
DEBUG: ParameterBinding Information: 0 :     Parameter [Name] PIPELINE INPUT ValueFromPipeline NO COERCION
DEBUG: ParameterBinding Information: 0 :     BIND arg [Name] to parameter [Name]
DEBUG: ParameterBinding Information: 0 :         Executing DATA GENERATION metadata: [System.Management.Automation.ArgumentTypeConverterAttribute]
DEBUG: ParameterBinding Information: 0 :             result returned from DATA GENERATION: Name
DEBUG: ParameterBinding Information: 0 :         BIND arg [Name] to param [Name] SUCCESSFUL
DEBUG: ParameterBinding Information: 0 : MANDATORY PARAMETER CHECK on cmdlet [Test-Pipeline]
DEBUG: ParameterBinding Information: 0 : BIND PIPELINE object to parameters: [Test-Pipeline]
DEBUG: ParameterBinding Information: 0 :     PIPELINE object TYPE = [System.String]
DEBUG: ParameterBinding Information: 0 :     RESTORING pipeline parameter's original values
DEBUG: ParameterBinding Information: 0 :     Parameter [Name] PIPELINE INPUT ValueFromPipeline NO COERCION
DEBUG: ParameterBinding Information: 0 :     BIND arg [Value] to parameter [Name]
DEBUG: ParameterBinding Information: 0 :         Executing DATA GENERATION metadata: [System.Management.Automation.ArgumentTypeConverterAttribute]
DEBUG: ParameterBinding Information: 0 :             result returned from DATA GENERATION: Value
DEBUG: ParameterBinding Information: 0 :         BIND arg [Value] to param [Name] SUCCESSFUL
DEBUG: ParameterBinding Information: 0 :     Parameter [Value] PIPELINE INPUT ValueFromPipeline NO COERCION
DEBUG: ParameterBinding Information: 0 :     BIND arg [Value] to parameter [Value]
DEBUG: ParameterBinding Information: 0 :         Executing DATA GENERATION metadata: [System.Management.Automation.ArgumentTypeConverterAttribute]
DEBUG: ParameterBinding Information: 0 :             result returned from DATA GENERATION: Value
DEBUG: ParameterBinding Information: 0 :         BIND arg [Value] to param [Value] SUCCESSFUL
DEBUG: ParameterBinding Information: 0 : MANDATORY PARAMETER CHECK on cmdlet [Test-Pipeline]
DEBUG: ParameterBinding Information: 0 : CALLING EndProcessing
DEBUG: ParameterBinding Information: 0 :     BIND NAMED cmd line args [Write-Host]
DEBUG: ParameterBinding Information: 0 :     BIND POSITIONAL cmd line args [Write-Host]
DEBUG: ParameterBinding Information: 0 :     BIND REMAININGARGUMENTS cmd line args to param: [Object]
DEBUG: ParameterBinding Information: 0 :         BIND arg [System.Collections.Generic.List`1[System.Object]] to parameter [Object]
DEBUG: ParameterBinding Information: 0 :             COERCE arg to [System.Object]
DEBUG: ParameterBinding Information: 0 :                 Parameter and arg types the same, no coercion is needed.
DEBUG: ParameterBinding Information: 0 :             BIND arg [System.Collections.Generic.List`1[System.Object]] to param [Object] SUCCESSFUL
DEBUG: ParameterBinding Information: 0 :     MANDATORY PARAMETER CHECK on cmdlet [Write-Host]
DEBUG: ParameterBinding Information: 0 :     CALLING BeginProcessing
Name: Value
DEBUG: ParameterBinding Information: 0 :     CALLING EndProcessing
DEBUG: ParameterBinding Information: 0 :     BIND NAMED cmd line args [Write-Host]
DEBUG: ParameterBinding Information: 0 :     BIND POSITIONAL cmd line args [Write-Host]
DEBUG: ParameterBinding Information: 0 :     BIND REMAININGARGUMENTS cmd line args to param: [Object]
DEBUG: ParameterBinding Information: 0 :         BIND arg [System.Collections.Generic.List`1[System.Object]] to parameter [Object]
DEBUG: ParameterBinding Information: 0 :             COERCE arg to [System.Object]
DEBUG: ParameterBinding Information: 0 :                 Parameter and arg types the same, no coercion is needed.
DEBUG: ParameterBinding Information: 0 :             BIND arg [System.Collections.Generic.List`1[System.Object]] to param [Object] SUCCESSFUL
DEBUG: ParameterBinding Information: 0 :     MANDATORY PARAMETER CHECK on cmdlet [Write-Host]
DEBUG: ParameterBinding Information: 0 :     CALLING BeginProcessing
Value: Value
DEBUG: ParameterBinding Information: 0 :     CALLING EndProcessing

Answer 1

根据 Lee Dailey 的评论，您只能让一个参数通过“值”接受来自管道的输入(对于每种值类型，例如字符串、整数等)。您的代码当前正在做的是发送一组字符串值，然后通过管道一次处理一个。

如果您想将多个值一起发送到管道中，您可以通过使这些值成为自定义对象的属性来实现，然后您可以使用 ValueFromPipelineByPropertyName 通过管道接受它们> 参数。这通过匹配与输入参数同名的输入对象的任何属性来实现:

function Test-Pipeline {
  [CmdletBinding ()]
  Param(
    [Parameter(ValueFromPipelineByPropertyName=$true)][String]$Name,
    [Parameter(ValueFromPipelineByPropertyName=$true)][String]$Value
  )
  Write-Host "Name: $Name"
  Write-Host "Value: $Value"
}

$MyObject = [pscustomobject]@{
    Name = "MyName"
    Value = "MyValue"
}

$MyObject | Test-Pipeline

结果:

Name: MyName
Value: MyValue

另一种类似的方法是使用 ValueFromPipeline 接受输入对象，然后从该对象获取属性值:

function Test-Pipeline {
  [CmdletBinding ()]
  Param(
    [Parameter(ValueFromPipeline=$true)][Object]$InputObject
  )

  $Name = $InputObject.Name
  $Value = $InputObject.Value

  Write-Host "Name: $Name"
  Write-Host "Value: $Value"
}

$MyObject = [pscustomobject]@{
    Name = "MyName"
    Value = "MyValue"
}

$MyObject | Test-Pipeline

某些 cmdlet 将同时支持这两种方法，因为 PowerShell 将首先尝试按对象类型进行匹配，然后恢复为按属性名称进行匹配。如果您想了解更多，这里有一个详细的解释:https://blogs.technet.microsoft.com/heyscriptingguy/2013/03/25/learn-about-using-powershell-value-binding-by-property-name/

请注意，如果您要通过管道成功处理值，您还需要在函数中使用 Process{} block ，这会导致一次处理一个对象集合:

function Test-Pipeline {
  [CmdletBinding ()]
  Param(
    [Parameter(ValueFromPipeline=$true)][Object]$InputObject
  )

  Process {
      $Name = $InputObject.Name
      $Value = $InputObject.Value

      Write-Host "Name: $Name"
      Write-Host "Value: $Value"
  }
}

$MyObject = @(
    [pscustomobject]@{
        Name = "MyName"
        Value = "MyValue"
    }
    [pscustomobject]@{
        Name = "MySecondName"
        Value = "MySecondValue"
    }
)

$MyObject | Test-Pipeline

如果没有这个，只会处理对象集合中的最后一个值。