Powershell functions, parameters and arg

Question

I write own powershell func for debug like:

function StartDebug {
    param (
        [PARAMETER(Mandatory = $true)]
        [ValidateNotNullOrEmpty()]
        $FunctionName,
        [PARAMETER(Mandatory = $false)]
        $OtherArg
    )

    try {& $FunctionName $OtherArg} catch {...} finally {...}

and use it everyway, but i need more arg after $FunctionName. is it realistic to pass many arguments in this case bec use from 0 to 10 arg. do I have to list all the arguments that can be in the parameters of the function? like:

function StartDebug {
    param (
        [PARAMETER(Mandatory = $true)]
        [ValidateNotNullOrEmpty()]
        $FunctionName,
        [PARAMETER(Mandatory = $false)]
        $OtherArg,
        [PARAMETER(Mandatory = $false)]
        $OtherArg1,
        [PARAMETER(Mandatory = $false)]
        $OtherArg2,
        [PARAMETER(Mandatory = $false)]
        $OtherArg3
    )

    try {& $FunctionName $OtherArg OtherArg1 OtherArg2 OtherArg3 } catch {...} finally {...}

but i dont use positional parameters in code and too many named parameters in code (~100)

Interested in any ideas about this. tnx!

score 0 · Accepted Answer · answered May 19 '21 at 10:04

The magic word is Splatting. You can provide an array or a hashtable containing your arguments to a function. The splatter is written with an @VariableName instead of the $:

function StartDebug {
    param (
        [PARAMETER(Mandatory = $true)]
        [ValidateNotNullOrEmpty()]
        $FunctionName,
        [PARAMETER(Mandatory = $false)]
        $OtherArg
    )

    try {& $FunctionName @OtherArg    # Watch out for the @ in the OtherArg
    } catch {$_} finally {}
}


$FunctionName = 'Get-ChildItem'

$Splatter = @{
    Path      = 'C:\'
    Filter    = 'Users'
    Directory = $true
}

$Splatter2 = @('c:\')

StartDebug $FunctionName $Splatter

StartDebug $FunctionName $Splatter2

However if you want to use single items as $OtherArg you will have to provide them as single element array as can be seen with $Splatter2. Or extend your function to transform single arguments in arrays automatically, but thats up to you.

Wow. It working. Сan you describe the process "transform single arguments in arrays" in more detail? — JustDj, May 19 '21 at 11:50
technically you have 2 options. 1. check `if` the `.count` of `$OtherArg` is high than 1 , then use `@` `else` use `$`. 2. if the `if` the `.count` is 1 place `$OtherArg` in `@()` like in `$Splatter2` or write `[array]$OtherArg` in both cases it will be cast to an array. — T-Me, May 20 '21 at 06:21

score 0 · Answer 2 · answered May 19 '21 at 10:08

I think you better run it using scriptblock:

$result = Invoke-DeepDebug { Get-ChildItem -Path 'C:\' ; Get-Service -InformationAction Continue}

And in Invoke-DeepDebug you can work with $Command.AST as deep and detailed as you want.

Function Invoke-DeepDebug {
    param(
        [Parameter(Mandatory=$true, Position=0)]
        [Scriptblock]$Command
    )

    Write-Host -f Cyan "Executing " -n
    Write-Host -f Magenta $Command.Ast.Extent.Text -n 
    Write-Host -f Yellow " ... " -n

    $result = $null
    try { 
        $result = Invoke-Command $Command -ErrorAction Stop
        Write-Host -f Green "OK!" 
    } catch { 
        Write-Host -f Red "Error"
        Write-Host -f Red "`t$($_.Exception.Message)"
    }
    return $result
}

Powershell functions, parameters and arg

2 Answers2

Linked