How to create new clone instance of PSObject object

Question

I want to create new instance of my custom PSObject. I have a Button object created as PSObject and I want to create new object Button2 which has the same members as Button

Answer 1

Starting from PowerShell v5, you can use Class. The problem with psobject.Copy() is, if you update the cloned object, then your template object's referenced properties will be also updated.

example:

function testTemplates
{
    $PSCustomObjectTemplate = New-Object PSCustomObject -Property @{
        List1 = [System.Collections.Generic.List[string]]@()  # will be updated in template
        String1 = "value1" # will not be updated in template
        Bool1 = $false # will not be updated in template
    }

    $objectFromPSTemplate1 = $PSCustomObjectTemplate.psobject.Copy()
    $objectFromPSTemplate1.List1.Add("Value")
    $objectFromPSTemplate1.String1 = "value2" 
    $objectFromPSTemplate.Bool1 = $true 

    # $PSCustomObjectTemplate IS updated, so CANNOT be used as a clean template!
    $PSCustomObjectTemplate

    Class ClassTemplate {
        [System.Collections.Generic.List[string]]$List1 = @() # will not be updated in template
        [string]$String1 = "value1" # will not be updated in template
        [bool]$Bool1 = $false # will not be updated in template
    }
    $objectFromClassTemplate = [ClassTemplate]::new()
    $objectFromClassTemplate.List1.Add("Value")
    $objectFromClassTemplate.String1 = "value2"
    $objectFromClassTemplate.Bool1 = $true

    # $ClassTemplate IS NOT updated, so can be used as a clean template!
    [ClassTemplate]::new()
}

testTemplates

PS C:\Windows\system32> testTemplates

List1   String1 Bool1
-----   ------- -----
{Value} value1  False       

-> Template from PSCustomObject is updated (referenced property -List1)

List1   String1 Bool1
-----   ------- -----
{}      value1  False       

-> Template from Class is safe

Answer 2

Based on the answer by @TeraFlux, here's a function that will do a deep copy on multiple objects and accepts pipeline input.

Note, it leverages json conversion with a default depth of 100, which lends it to a few weaknesses

• It's going to be slow on deep or complex objects, or objects with expensive (slow) pseudoproperties (methods pretending to be properties that are calculated on the fly when asked for)
  • Though it should still be faster than the Add-Member approach because the heavy lifting is going through a compiled function
• Anything that can't be stored in JSON may get corrupted or left behind (methods will be a prime candidate for this type of error)
  • Though any object that can safely go through this process should be savable, able to be safely stored (for recovery) or exported for transportation

I would be interested in any caveats or improvements to deal with these

function Clone-Object 
    {
    [CmdletBinding()]
    Param `
        (
        [Parameter(ValueFromPipeline)] [object[]]$objects,
        [Parameter()] [int] $depth = 100
        )
    $clones = foreach
        ($object in $objects)
        {
        $object | ConvertTo-Json -Compress -depth $depth | ConvertFrom-Json
        }
    return $clones
    }

Here are some very basic unit tests

$testClone = `
    {
    $test1 = $null
    $test2 = $null
    $test3 = $null

    $Test1 = [psCustomObject]@{a=1; b=2; c=3; d=4}
    $Test2 = $Test1 | ConvertTo-Json -depth 100 | ConvertFrom-Json
    $Test2 | add-Member -Name "e" -Value "5" -MemberType noteproperty
    $Test3 = $test2 | Clone-Object
    $Test3 | add-Member -Name "f" -Value "6" -MemberType noteproperty
    $Test1.a = 7
    $Test2.a = 8

    #$Expected0 = [psCustomObject]@{a=1; b=2; c=3; d=4}
    $Expected1 = [pscustomobject]@{a=7; b=2; c=3; d=4}
    $Expected2 = [pscustomobject]@{a=8; b=2; c=3; d=4; e=5}
    $Expected3 = [pscustomobject]@{a=1; b=2; c=3; d=4; e=5; f=6}

    $results1 = @(); $results1+=$test1; $results1+=$expected1
    $results2 = @(); $results2+=$test2; $results2+=$expected2
    $results3 = @(); $results3+=$test3; $results3+=$expected3
    $results1 | Format-Table # if these don't match then its probably passing references (copy not clone)
    $results2 | Format-Table # if these don't match the core approach is incorrect
    $results3 | Format-Table # if these don't match the function didn't work

    }
&$testClone

Answer 3

For some reason PSObject.Copy() doesn't work for all object types. Another solution to create a copy of an object is to convert it to/from Json then save it in a new variable:

$CustomObject1 = [pscustomobject]@{a=1; b=2; c=3; d=4}
$CustomObject2 = $CustomObject1 | ConvertTo-Json -depth 100 | ConvertFrom-Json
$CustomObject2 | add-Member -Name "e" -Value "5" -MemberType noteproperty

$CustomObject1 | Format-List
$CustomObject2 | Format-List