How to return a reference value with a method from an extended Powershell object?

Question

I'm trying to extend a Powershell object with a method that

returns a true or false to indicate success
outputs a value by reference ([ref])

I have in my module MyExtensions.psm1.

Update-TypeData -TypeName [MyType] -MemberType ScriptMethod -memberName TryGetValue -force -value `
{
    param(
        $myInput,
        [ref]$myOutput
    )

    try
    {
        # do something with $myInput
        $myOutput = …
        return $true
    }
    catch
    {
        return $false
    }

}

The goal is to be able to write in a script or in another module:

Import-Module MyExtensions
$myInput = …
$value = $null
if($myTypeItem.TryGetValue($myInput, $value)
{
  # I know that the $value is good
}

JPBlanc · Accepted Answer · 2020-04-28 15:20:15Z

1

Using argument by reference (you just miss $myOutput.Value ="")

function addition ([int]$x, [int]$y, [ref]$R)
{
 $Res = $x + $y
 $R.value = $Res
}

$O1 = 1
$O2 = 2
$O3 = 0
addition $O1 $O2 ([ref]$O3)
Write-Host "values from addition $o1 and $o2 is $o3"

A more comple answer here.

answered Apr 28, 2020 at 15:20

JPBlanc

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1 Comment

Juha Metsäkallas Over a year ago

Awesome, thanks! So all I had missing was $myOutput.value = … in MyExtensions.psm1 and the call should be if($myTypeItem.TryGetValue($myInput, [ref]$value).

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