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How can i force a Powershell function to return an Array?
This simple function for Example, if "C:\New folder" contains only 1 element, it will not return an Array. 

function Get-AlwaysArray
{
    $returnArray = gci "C:\New folder"
    Write-Output $returnArray
}
(Get-AlwaysArray).Gettype()

There is already a Thread with a pretty good upvoted answer here But non of the answer works unfortunally.
Here is what i have tried:

function Get-AlwaysArray {
    [Array]$returnArray = gci "C:\New folder"
    Write-Output $returnArray   
}
(Get-AlwaysArray).Gettype()

function Get-AlwaysArray {
    $returnArray = @(gci "C:\New folder")
    Write-Output @($returnArray)   
}
(Get-AlwaysArray).Gettype()

function Get-AlwaysArray {
    $returnArray = @(gci "C:\New folder")
    Write-Output @($returnArray | Where-Object {$_})   
}
(Get-AlwaysArray).Gettype()

function Get-AlwaysArray {
    [Object[]]$returnArray = @(gci "C:\New folder")
    Write-Output @($returnArray | Where-Object {$_})   
}
(Get-AlwaysArray).Gettype()

The only way it would work is 

function Get-AlwaysArray {
    $returnArray = gci "C:\New folder"
    Write-Output $returnArray 
}
@(Get-AlwaysArray).Gettype()

But i dont want to add this, everytime i call my function.
What am i doing wrong?

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1
  • I think you should not try to encapsulate this. PowerShell's pipeline output is build around the premise you are trying to avoid. I would always surround with @() where I need to use the output and it is needed as an array. Commented Dec 16, 2019 at 15:04

2 Answers 2

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13

First, use the array sub-expression operator @( ... ). This operator returns the result of one or more statements as an array. If there is only one item, the array has only one member.

$returnArray = @( Get-ChildItem "F:\PowerShell\A" )

Use Write-Output with the switch -NoEnumerate to prevent PowerShell from un-rolling the array. 

Write-Output -NoEnumerate $returnArray

You can also effectively achieve the same result using Write-Output without using the -NoEnumerate by using the following syntax below. 

Write-Output ,$returnArray

The comma in front of $returnArray effectively creates a new array with $returnArray as its only element. PowerShell then un-rolls this new single-element array, returning the original $returnArray intact to the caller.

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1 Comment

Nice systematic overview, but note that you need parens in the last command: Write-Output (,$returnArray) or - better yet - omit the Write-Output and use just , $returnArray.
-2

try this one,

function Get-AlwaysArray
{

    $returnArray = Get-ChildItem "F:\PowerShell\A"
    Write-Output $()$returnArray
}

(Get-AlwaysArray).Gettype()

IsPublic IsSerial Name                                     BaseType                                                                  
-------- -------- ----                                     --------                                                                  
True     True     Object[]                                 System.Array
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3 Comments

Bad idea, this will always add a$Null as the first item to your array.
Good point, @iRon. In addition to the unwanted $null, the approach is ineffective in Windows PowerShell. Only in PowerShell Core (v6+) do you get $returnArray as a single output object (as the 2nd output object after the unwanted $null).
@trampCoder: To (indirectly) show that $null is being added, try function foo() { Write-Output $() (1,2) }; foo | % { "[$_]" } (inside an expandable string, $null expands to an empty string).

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