PowerShell array getting new entries - arrays

Question

In this snippet I have a function (FDiskScan) that gets a computer name as an input and should return an array of objects.
function FDiskScan ([String] $name)
{
$outarray = [System.Collections.ArrayList]#()
$diskscan = Get-WmiObject Win32_logicaldisk -ComputerName $name
foreach ($diskobj in $diskscan)
{
if($diskobj.VolumeName -ne $null )
{
$max = $diskobj.Size/1024/1024/1024
$free = $diskobj.FreeSpace/1024/1024/1024
$full = $max - $free
$obj = #{
'ID' = $diskobj.deviceid
'Name' = $diskobj.VolumeName
'TotalSpace' = $max
'FreeSpace' = $free
'OccupiedSpace' = $full }
$TMP = New-Object psobject -Property $obj
$outarray.Add($TMP)
}
}
return $outarray
}
$pc = "INSERT PC NAME HERE"
$diskdata = [System.Collections.ArrayList]#()
$diskdata = FDiskScan($pc)
foreach ($disk in $diskdata)
{
Write-Host "Disco: " $disk.ID
Write-Host "Espaço Total: " ([math]::Round($disk.TotalSpace, 2)) "GB"
Write-Host "Espaço Ocupado: " ([math]::Round($disk.OccupiedSpace, 2)) "GB"
Write-Host "Espaço Livre" ([math]::Round($disk.FreeSpace, 2)) "GB" "`n"
}
Within the function with debugging and going into the variables I can see that everything is alright, and when the array gets out of the function and into the script scope it adds 2 more entries.
While in debug mode it tells me that $outarry within FDiskScan has the two disks that I have on my system organised as they should be.
However on:
$diskdata = FDiskScan($pc)
It says that it has an entry of value 0 on index 0 and of value 1 on index 1, then the disks follow suit, first disk C: in index 3 and disk D in index 4.
The expected behaviour was for index 0 and 1 having disks C and D respectively not a phantom 0 and 1 entries.

Answer 1

When adding an object to an array list in PowerShell (i.e. $outarray.Add($TMP)) the index, the object was added at, gets returned. As you don't assign the return value to a variable the function returns a System.Array containing the indexes and the entries of the array list returned by return $outarray. That's the reason why your functions return value contains 4 elements. Furthermore your functions return value in this case is not of type System.Collections.ArrayList but of type System.Array.
To avoid that behaviour do the following.
$null = $outarray.Add($TMP);

Answer 2

You are seeing 0, 1 because of this line - $outarray.Add($TMP). Change it to $outarray.Add($TMP) | Out-Null. I think PowerShell is printing the index when adding to the array.