如何从变量调用Powershell函数

Question

I want to create a function to call a function with parameters and output the results of the called function.

Working Code:

$MockDataPath = 'C:\temp'
$MockDataFunctionName = 'Get-SomeFunction'
$Results = Get-SomeFunction -Parameter1 'SomeParameter'
$Results | Export-CliXML "$MockDataPath\$MockDataFunctionName.xml"

What I want to do: The first $Results = line is where I'm having the issue. I know it does not work but I have been unable to find a solution online. I'm also unsure if the $MockFunctionParameters is the correct approach for parameter passing.

Function Get-MockedData {
  [CmdletBinding()]
  param(
    [Parameter(
      Position = 0,
      Mandatory = $true,
      ValueFromPipelineByPropertyName = $true,
      HelpMessage = "Enter the name of the function you want to get mock data from.  Ex: Get-GenericCredential")]
    [ValidateNotNullOrEmpty()]
    [string]
    $MockFunctionName,

    [Parameter(
      Mandatory = $false,
      ValueFromPipelineByPropertyName = $true,
      HelpMessage = "Enter the parameters of the function you want to get mock data from.  Ex: '-Parameter1 SomeParameter'")]
    [ValidateNotNullOrEmpty()]
    [string]
    $MockFunctionParameters,

    [Parameter(
      Mandatory = $false,
      ValueFromPipelineByPropertyName = $true,
      HelpMessage = "Enter the directory you want the mocked data to appear.  Default: 'C:\temp'")]
    [ValidateNotNullOrEmpty()]
    [string]
    $MockDataOutputPath = 'C:\temp'
  )

  $Results = $MockFunctionName $MockFunctionParameters
  $Results | Export-Clixml "$MockDataOutputPath\$MockDataFunctionName.xml"
}

Answer 1

You're going to need to use Splatting rather than passing the parameters as a string. So you'd call it as Get-MockedData -MockFunctionName <name> -MockFunctionParameters @{Parameter1 = "SomeParameter}

Then you call the function in $Result using & .

$Results = &$MockFunctionName @MockFunctionParameters

Bruce Payette pointed out that Invoke-Expression is considered harmful (and in this case could result in injection because you're passing arbitrary parameters and functions).

---

Alternately, you can use DynamicParameters and actually have it include the parameters from the original function (Which will still work with splatting as above but also allows clearer functionality when using interactively).

It doesn't have full functionality but does offer tab completion for parameters (it has a few issues there such as get-content not showing -path but completing -pa<tab> into -path ) although it will not always offer tab completion with ValidationSet (It works on a custom function but failed on New-Item -itemtype so it might be an issue with built-in commands). It does not need -MockFunctionParameters since those parameters can be splatted ( $splat = @{path = "test.xml"} ) directly in to the function call Get-MockedData get-content @splat .

function Get-MockedData {
    [cmdletbinding()]
    param(
        [Parameter(
            Position = 0,
            Mandatory = $true,
            ValueFromPipelineByPropertyName = $true,
            HelpMessage = "Enter the name of the function you want to get mock data from.  Ex: Get-GenericCredential")]
        [ValidateNotNullOrEmpty()]
        [ValidateScript( {Get-Command $_})]
        [string]
        $MockFunctionName,

        [Parameter(
            Mandatory = $false,
            ValueFromPipelineByPropertyName = $true,
            HelpMessage = "Enter the directory you want the mocked data to appear.  Default: 'C:\temp'")]
        [ValidateNotNullOrEmpty()]
        [string]
        $MockDataOutputPath = 'C:\temp'
    )
    DynamicParam {
        if ($MockFunctionName) {
            $base = get-command $MockFunctionName -ErrorAction SilentlyContinue
        }
        if ($base) {
            $dict = new-object System.Management.Automation.RuntimeDefinedParameterDictionary
            $base.Parameters.GetEnumerator() | ForEach-Object {
                $val = $_.value
                $key = $_.key
                if ($key -notin [System.Management.Automation.Internal.CommonParameters].GetProperties().name) {
                    $param = New-Object System.Management.Automation.RuntimeDefinedParameter($key, $val.parameterType, $val.attributes)
                    $dict.add($key, $param)
                }
            }
            return $dict
        }
    }
    Begin {
        # Get a list of own parameters to exclude later
        $self = Get-Command Get-MockedData
        $selfParams = $self.parameters.keys | Where-Object {
            $_ -notin [System.Management.Automation.Internal.CommonParameters].GetProperties().name -and
            -not $self.parameters.$_.isdynamic
        }
    }
    Process {
        # Hashtable to hold valid parameters
        $splatParams = @{}

        # Remove own parameters
        $psboundparameters.keys | where-object {$_ -notin $selfParams} | ForEach-Object {
            $splatParams.add($_, $psboundparameters[$_])
        }

        $results = &$MockFunctionName @splatParams
        $Results | Export-Clixml "$MockDataOutputPath\$MockDataFunctionName.xml"
    }
}

Answer 2

You need to use the call operator & to indirectly call a function. In the second last line of your function put '&' before $MockFunctionName as in

  $Results = & $MockFunctionName $MockFunctionParameters

Parameters are trickier - there you should look at splatting to see how to pass parameters.

Finally, you might want to look at how Pester handles mocking .