Is it possible to create an anonymous Recursive Function in PowerShell? (if yes, how?)

I have a recursive object and using a recursive function to drill down through the properties, like:

$Object = ConvertFrom-Json '
{
    "Name" : "Level1",
    "Folder" : {
        "Name" : "Level2",
        "Folder" : {
            Name : "Level3"
        }       
    }
}'

Function GetPath($Object) {
    $Object.Name
    if ($Object.Folder) { GetPath $Object.Folder }
}

(GetPath($Object)) -Join '\'

Level1\Level2\Level3

The function is relative small and only required ones, therefore I would like to directly invoke it as an anonymous function, some like:

(&{
    $Object.Name
    if ($Object.Folder) { ???? $Object.Folder }
}) -Join '\'

Is this possible in PowerShell? If yes, how can I (as clean as possible) refer to the current function at ?????

CodePudding user response：

Unfortunately there is not much documentation on this topic but you could execute the anonymous script block by calling $MyInvocation.MyCommand.ScriptBlock, a simple example:

& {
    param([int] $i)

    if($i -eq 10) { return $i }
    ($i  )
    & $MyInvocation.MyCommand.ScriptBlock $i
}

# Results in 0..10

Using your current code and Json as example:

(& {
    param($s)

    $s.Name
    if ($s.Folder) { & $MyInvocation.MyCommand.ScriptBlock $s.Folder }
} $Object) -Join '\'

# Results in Level1\Level2\Level3

A bit more code but the same can be accomplished using a Collections.Queue instead of recursion, which is likely to be a more resource efficient way:

$(
    $queue = [System.Collections.Queue]::new()
    $queue.Enqueue($object)
    while($queue.Count) {
        $node = $queue.Dequeue()
        $node.Name
        if($node.Folder) { $queue.Enqueue($node.Folder) }
    }
) -Join '\'

CodePudding user response：

@Santiago's helpful answer was exactly where I was initially looking for.
Nevertheless, it doesn't always require a recursive function to crawl through a recursive object.
As in the mcve, I could just have done:

@(
    do {
        $Object.Name
        $Object = $Object.Folder
    } while ($Object)
) -Join '\'