PS管道多参数绑定

Question

我试图通过管道将两个参数传递给函数，但它似乎不像预期的那样工作，而且我很难理解其中的原因。

米维

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

名称:价值 价值:价值

我试着运行Trace-Command命令来查看发生了什么。在第35行中，我们可以看到Value绑定到$Parameter。

为什么PowerShell要将第二个输入绑定到这两个参数？如果这是预期的，为什么只发生在第二个参数而不是第一个参数？

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的注释，您只能有一个参数接受管道中的" value“输入(对于每个值类型，例如string、int等)。您的代码当前所做的是发送一个字符串值数组，然后通过管道一次处理一个字符串值。

如果要将多个值一起发送到管道中，可以将这些值设置为自定义对象的属性，然后可以通过管道使用ValueFromPipelineByPropertyName参数接受这些值。这是通过匹配与输入参数具有相同名称的输入对象的任何属性来实现的：

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

另一种但类似的方法是使用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

有些cmdlet将支持这两种方法，因为PowerShell将首先尝试按对象类型匹配，然后根据属性名称恢复到匹配。如果您想知道更多的话，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/

注意，如果要通过管道成功地处理值，还需要在函数中使用Process { }块，这将导致每次只处理一个对象集合：

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

如果没有这一点，将只处理对象集合中的最后一个值。

Answer 2

除了@Mark的答案之外，正如前面提到的，ValueFromPipeline属性只能在每个参数类型中设置一次。

这是使用多个ValueFromPipeline的示例，每个示例用于不同的参数类型。

每次迭代只分配一个参数。与输入值类型匹配的类型。

注意：

当初始化时不使用特定值时，$Int将包含0。

检查使用了哪个参数集更安全，而不仅仅是在赋值的情况下。

function testus() {
  param(
    [Parameter(ValueFromPipeline, ParameterSetName = "A")]
    [String]$Str,
    [Parameter(ValueFromPipeline, ParameterSetName = "B")]
    [Int]$Int
  )
  process {
    if ($PSCmdlet.ParameterSetName -eq 'A') {
        Write-Host ""
        Write-Host "String was used:"
        Write-Host "Str: $Str"
        Write-Host "(Int contains initialized default value '0': $Int)"
    } elseif ($PSCmdlet.ParameterSetName -eq 'B') {
        Write-Host ""
        Write-Host "Integer was used:"
        Write-Host "Int: $Int"
        Write-Host "(Str contains initialized default value '' (empty string): $($Str.gettype().FullName))"
    }
  }
}

'a', 1, 0 | testus