ValueFromPipeline behavior?

Question

I have a command Get-Testdata that retrieves test data from different sources and stores these into a PSObject with the different values as properties. The total number of objects are then stored as an array, for easy manipulation, sorting, calculating etc.

My problem is that I want to be able to present this data as (color-coded) HTML, for which I've written another command, Show-TestResults. The input parameter looks like this

[Parameter(Mandatory=$true,Position=0,ValueFromPipeline=$true)]
[PSObject[]]$InputObject

UPDATE 1

This function itself is very basic, it simply sets some parameters for ConvertTo-HTML and then pipe the objects into that command:

$head = "<style>[...]" #styling with javascript etc
$header = "<H1>Test Results</H1>
$title = "Test results"
$InputObject | ConvertTo-HTML -head $head -body $header -title $title | Out-File $Filename

END UPDATE 1

However, when I try to use the ValueFromPipeline property, using the call

Get-Testdata [...] | Show-TestResults 

only the first object in the array is shown. But if I instead call the command like

$td = Get-Testdata [...]
Show-TestResults $td 

The whole array is presented, as expected. Can someone explain this - and hopefully guide me into correcting it?

Answer 1

If an advanced function is the requirement then I would go in the way proposed by @stej.

Otherwise I would consider this simple technique when a function accepts both pipeline and parameter input:

function Show-Data
(
    $FileName,
    $InputObject
)
{
    # this is the trick:
    if ($InputObject) { $input = $InputObject }

    # process the input (from pipeline or parameter)
    $input | ConvertTo-HTML > $FileName
}

# pipe data
Get-ChildItem | Show-Data Test1.htm

# pass via parameter
Show-Data Test2.htm (Get-ChildItem)

---

N.B. $input in this case is an automatic variable for the pipeline input.

Answer 2

You probably process data in end block, not process block.

Look at an example:

function getdata {
    1
    2
    3
    4
}
function show-data {
    param(
        [Parameter(mandatory=$true, ValueFromPipeline=$true)]$InputObject,
        [Parameter(mandatory=$true)]$FileName
    )

    # this is process block that is probably missing in your code
    begin { $objects = @() }
    process { $objects += $InputObject }
    end {
        $head = "<style></style>"
        $header = "<H1>Test Results</H1>"
        $title = "Test results"
        $objects | ConvertTo-HTML -head $head -body $header -title $title | Out-File $Filename
    }
}

getdata | show-data -file d:\temp\test.html