Flattening structures in PowerShell

flatten.md

Quickly coding a function that allows flattening a structure. The goal is to use in comparing complex structures, such as created by the ConvertFrom-JSON or ConvertFrom-Yaml.

Outputs a hash table.

Example:

$res = Flatten-Object @{SH = @("bin", "bash"); A = 1; B = "ZZ"; C = @{CC = "CC"}; Logic = $true}
$res.Keys | Sort-Object | % { Write-Output "$_ = $($res[$_])"}

Outputs:

.A = 1
.B = ZZ
.C.CC = CC
.Logic = True
.SH[0] = bin
.SH[1] = bash

flatten.ps1

function Flatten-Object ( $obj, [string] $prefix = "" ) {
    [CmdletBinding()]

    $res = @{}
    Write-Verbose $prefix

    if ($null -eq $obj) {
        return @{$prefix = "null"}
    } 

    switch -Regex ($obj.GetType().Name )
    {
        '^(Boolean|String|Int32|Int64|Float|Double)$' {
            $res += @{$prefix = $obj}
        }
        "Hashtable" {
            $obj.GetEnumerator() | ForEach-Object {
                $res += Flatten-Object $_.Value ($prefix+"."+$_.Key)
            }
        }
        '^(List.*|.+\[\])$' {
            $i = 0
            foreach ( $entry in $obj ) {
                $ind = $prefix + "[$i]"
                $res += Flatten-Object $entry $ind
                $i++
            }
        }
    }
    $res
}