How to dynamically reference a powershell variable - arrays

Question

I have an array that contains different rows where one column identifies the "record" "type." I want to iterate through this array and sort each item based on that value into a new array so that I have one array per type.
Here's what I have so far:
$data = Get-ADObject -SearchBase $sb -filter * -properties * | select samaccountname,canonicalname,objectclass,distinguishedname | sort objectclass,samaccountname
$oct = $data | select objectclass -Unique
foreach ($o in $oct)
{
$oc = $o.objectclass
Remove-Variable -name "$oc"
New-Variable -name "$oc" -value #()
}
$d = #()
$user = #()
foreach ($d in $data)
{
$oc = $d.objectclass
foreach ($o in $oct)
{
$1 = $o.objectclass
if ($1 -eq $oc)
{
('$' + $oc) += $d
}
}
}
(the lines: Remove-Variable -name "$oc", $d = #(), and $user = #() are for testing purposes so ignore those)
This works great up to the line where I try to dynamically reference my new arrays. What am I doing wrong and how can I fix it?
The error text is:
('$' + $oc) += $d
~~~~~~~~~ The assignment expression is not valid. The input to an assignment operator must be an object that is able to accept
assignments, such as a variable or a property.
CategoryInfo : ParserError: (:) [], ParentContainsErrorRecordException
FullyQualifiedErrorId : InvalidLeftHandSide
I have tried using $($oc), but that didn't work either. If I change it to the name of one of my dynamically created arrays like $user, the code works fine except that it loads everything into the $user array (obviously).
The reason I tried ('$' + $oc) is because this is the only way I could get ISE to output $user.
I also tried ('$' + $oc).add($d) but it appears to be seeing it as a string rather than the array.
Any pointers are appreciated.

Answer 1

Use the Get-Variable and Set-Variable cmdlets:
$curVal = Get-Variable -Name $oc -ValueOnly
Set-Variable -Name $oc -Value ($curVal+$d)
But note that you would be better off building this array in a local variable first, and then assigning it to your "runtime-named" variable once, as these get and set operations are going to be way slower.

Answer 2

Rather than fiddling around with dynamically named variables, I'd use dictionary-type, like for example a hashtable:
# initialize an empty hashtable
$objectsByClass = #{}
# Define list of properties
$properties = 'samaccountname','canonicalname','objectclass','distinguishedname'
# Retrieve AD objects
$Data = Get-ADObject -SearchBase $sb -filter * -properties $properties | select $properties | sort objectclass,samaccountname
#Populate hashtable
$Data |ForEach-Object {
if(-not $objectsByClass.ContainsKey($_.objectClass)){
# Create entry in hashtable
$objectsByClass[$_.objectClass] = #()
}
# Add entry to dictionary
$objectsByClass[$_.objectClass] += $_
}
Now you can access the items by class name:
$users = $objectsByClass['user']
And you can easily discover all class names:
$classNames = $objectsByClass.Keys
As briantist points out, you can also have Group-Object build the hashtable for you if the above gets too verbose:
$objectsByClass = $Data |Group-Object objectClass -AsHashTable