Windows PowerShell - Array to function

Question

I have this problem which makes me crazy:

i have a function like

function xyz
{
    foreach($x in $input)
    {
    }
}

1..10 | xyz

this is saved in a file test.ps1. When I execute it like ".\test.ps1" every time it writes that

cmdlet Write-Output at command pipeline position 1
Supply values for the following parameters:
InputObject[0]:

Why it is so? It does not work if I do like

$myArray = @("a","b","c")
xyz -arr $myArray

and doing a function like

function xyz
{
    param(
        [string[]]$arr
    )

    foreach($x in $arr)
    {
    }
}

Why?

I did the code that you said prompted you for input and it worked just fine for me. — EBGreen
– EBGreen, Commented Dec 6, 2012 at 16:35
there was another error i just missed, the reason of that was that there was function in the function and in that function i wanted echo something, but there was just "echo" without the argument, i am from unix environment and when you type "echo" there without parameters, it just writes empty line and this trick does not work in PS ... what a stupid mistake :D — stewenson
– stewenson, Commented Dec 7, 2012 at 9:51
The answer selected does not answer the question. I came along with the same problem and was not helped by it. You have answered the question in your comment above, it would seem more appropriate to add that as an answer and select it. — Jacxel
– Jacxel, Commented Nov 13, 2013 at 17:54

Keith Hill · Accepted Answer · 2012-12-06 16:38:27Z

I can't duplicate the error you're seeing but in general, when you want to process pipeline input the easiest way is like this:

function xyz
{
    process {
        $_
    }
}

1..10 | xyz

The process block will get called for every object in the pipeline. In fact, this is a common enough pattern that PowerShell has an even more convenient shortcut called a filter e.g.:

filter xyz
{
    $_
}

1..10 | xyz

Now if you need to handle regular parameters as well as pipeline input, then you need to add a param declaration and used advanced function parameter functionality e.g.:

function xyz
{
    param(
        [Parameter(Mandatory=$true, Position=0, ValueFromPipeline=$true)]
        [object[]]
        $myparam
    )
    process {
       foreach ($elem in $myparam)
       {
           $elem
       }
    }
}

xyz (1..10)
'a','b','c' | xyz

This works for both pipeline input and simple parameter (non-pipeline) usage. This most closely emulates how binary cmdlets actually work.

Collectives™ on Stack Overflow

Windows PowerShell - Array to function

1 Answer 1

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Related