PowerShell
PowerShellの動的パラメータ

「シンプルな」動的パラメータ

この例では、 $SomeUsefulNumberが5より大きい場合、MyTestFunctionに新しいパラメータを追加します。

function MyTestFunction
{
    [CmdletBinding(DefaultParameterSetName='DefaultConfiguration')]
    Param
    (
        [Parameter(Mandatory=$true)][int]$SomeUsefulNumber
    )

    DynamicParam
    {
        $paramDictionary = New-Object -Type System.Management.Automation.RuntimeDefinedParameterDictionary
        $attributes = New-Object System.Management.Automation.ParameterAttribute
        $attributes.ParameterSetName = "__AllParameterSets"
        $attributes.Mandatory = $true
        $attributeCollection = New-Object -Type System.Collections.ObjectModel.Collection[System.Attribute]
        $attributeCollection.Add($attributes)
        # If "SomeUsefulNumber" is greater than 5, then add the "MandatoryParam1" parameter
        if($SomeUsefulNumber -gt 5)
        {
            # Create a mandatory string parameter called "MandatoryParam1"
            $dynParam1 = New-Object -Type System.Management.Automation.RuntimeDefinedParameter("MandatoryParam1", [String], $attributeCollection)   
            # Add the new parameter to the dictionary
            $paramDictionary.Add("MandatoryParam1", $dynParam1)
        }
        return $paramDictionary
    }

    process
    {
        Write-Host "SomeUsefulNumber = $SomeUsefulNumber"
        # Notice that dynamic parameters need a specific syntax
        Write-Host ("MandatoryParam1 = {0}" -f $PSBoundParameters.MandatoryParam1)
    }

}

使用法：

PS >  MyTestFunction -SomeUsefulNumber 3
SomeUsefulNumber = 3
MandatoryParam1 =

PS >  MyTestFunction -SomeUsefulNumber 6
cmdlet MyTestFunction at command pipeline position 1
Supply values for the following parameters:
MandatoryParam1:

PS >MyTestFunction -SomeUsefulNumber 6 -MandatoryParam1 test
SomeUsefulNumber = 6
MandatoryParam1 = test

2番目の使用例では、パラメータが欠落していることを明確に確認できます。

動的パラメータも自動補完で考慮されます。
行の最後にCtrl +スペースを押すと、次のようになります。

PS >MyTestFunction -SomeUsefulNumber 3 -<ctrl+space>
Verbose              WarningAction        WarningVariable      OutBuffer
Debug                InformationAction    InformationVariable  PipelineVariable
ErrorAction          ErrorVariable        OutVariable

PS >MyTestFunction -SomeUsefulNumber 6 -<ctrl+space>
MandatoryParam1      ErrorAction          ErrorVariable        OutVariable
Verbose              WarningAction        WarningVariable      OutBuffer
Debug                InformationAction    InformationVariable  PipelineVariable