Adding multiple ScriptMethods to PSCustomObject causes an invocation to be called multiple times

I have a basic PSCustomObject that I want to add multiple ScriptMethods to. When I invoke any ScriptMethod it is called a number of times equal to the number of ScriptMethods I added. Here’s a slimmed example:

function GetCustomObject {
    
    param(
        [Parameter(Mandatory=$true)] [String]$data
    )
    
    $CustomObject = [PSCustomObject]@{
        member = $data
    }

    $CustomObject | Add-Member -MemberType ScriptMethod -PassThru -Name PrintMember -Value {
        Write-Host "Data is:" $this.member
        $this.member += ", again?"
    }

    $CustomObject | Add-Member -MemberType ScriptMethod -PassThru -Name SomeOtherFunction -Value {
        Write-Host "SomeOtherFunction"
    }

    #Delete this ScriptMethod to reduce the number of prints by 1
    $CustomObject | Add-Member -MemberType ScriptMethod -PassThru -Name YetAnotherFunction -Value {
        Write-Host "YetAnotherFunction"
    }
}


$LocalCustomObject = GetCustomObject "Hello World"

$LocalCustomObject.PrintMember()

$LocalCustomObject.SomeOtherFunction()

$LocalCustomObject.YetAnotherFunction()

This code returns the following:

Data is: Hello World
Data is: Hello World, again?
Data is: Hello World, again?, again?
SomeOtherFunction
SomeOtherFunction
SomeOtherFunction
YetAnotherFunction
YetAnotherFunction
YetAnotherFunction

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I think it has something to do with how I’m adding the ScriptMethods to the PSCustomObject, but I have not yet figured it out. If you have a better way of adding ScriptMethods I’m all ears.

>Solution :

The issue is that you’re using -PassThru so your function is returning 3 objects instead of 1, and calling the methods over each member of the resulting array is possible due to member-access enumeration. Simply remove -PassThru from your code and output the object in the end:

function GetCustomObject {
    param(
        [Parameter(Mandatory = $true)] [String]$data
    )

    $CustomObject = [PSCustomObject]@{
        member = $data
    }

    $CustomObject | Add-Member -MemberType ScriptMethod -Name PrintMember -Value {
        Write-Host 'Data is:' $this.member
        $this.member += ', again?'
    }

    $CustomObject | Add-Member -MemberType ScriptMethod -Name SomeOtherFunction -Value {
        Write-Host 'SomeOtherFunction'
    }

    #Delete this ScriptMethod to reduce the number of prints by 1
    $CustomObject | Add-Member -MemberType ScriptMethod -Name YetAnotherFunction -Value {
        Write-Host 'YetAnotherFunction'
    }

    $CustomObject
}


$LocalCustomObject = GetCustomObject 'Hello World'
$LocalCustomObject.PrintMember()
$LocalCustomObject.SomeOtherFunction()
$LocalCustomObject.YetAnotherFunction()

You could also use -PassThru but only on the last Add-Member call:

function GetCustomObject {
    param(
        [Parameter(Mandatory = $true)] [String]$data
    )

    $CustomObject = [PSCustomObject]@{
        member = $data
    }

    $CustomObject | Add-Member -MemberType ScriptMethod -Name PrintMember -Value {
        Write-Host 'Data is:' $this.member
        $this.member += ', again?'
    }

    $CustomObject | Add-Member -MemberType ScriptMethod -Name SomeOtherFunction -Value {
        Write-Host 'SomeOtherFunction'
    }

    #Delete this ScriptMethod to reduce the number of prints by 1
    $CustomObject | Add-Member -MemberType ScriptMethod -Name YetAnotherFunction -Value {
        Write-Host 'YetAnotherFunction'
    } -PassThru
}


$LocalCustomObject = GetCustomObject 'Hello World'
$LocalCustomObject.PrintMember()
$LocalCustomObject.SomeOtherFunction()
$LocalCustomObject.YetAnotherFunction()