PowerShell: Difference [array] vs [array[]]

Question

I need to declare an array parameter in an called PS script. The array coming in from the caller/source script is in a hash table:

$Array = @(1, 2, 3)
$myHashTable = @{myArr = $Array}

Call: Z:\called.ps1 $myHashTable

In 'called.ps1', what is the difference between

Param(
$myArr
)

,

Param(
[array] $myArr
)

and

Param(
[array[]] $myArr
)

?

Answer 1

You can test that fairly directly. [grin] your examples give ...

• any type = remains that type
• 1d array = converts to an array if not one already
• 2d array = converts to a jagged array (array of arrays) if not one already

demo code ...

function Test-Parameter
    {
    Param
        (
        $GenericVar,
        [array]$OneD_Array,
        [array[]]$TwoD_Array
        )

    $GenericVar.GetType()
    $OneD_Array.GetType()
    $TwoD_Array.GetType()
    }

Test-Parameter -GenericVar 'One' -OneD_Array 'Two' -TwoD_Array 'Three'

output ...

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