New-Object PSObject works in PS script but not inside a function

Question

I am seeing strange results when using New-Object PSObject inside a PS function. I have searched and can't find any clues to why.

This works:

$b = "ValueB"
$c = "ValueC"

$H = @{
b = $b
c = $c
}

$z = $h | ConvertTo-Json

Write-Host $z

Output:

{
"c": "ValueC",
"b": "ValueB"
}

This does not work:

Function A {

PARAM ($b, $c)

$H = @{
b = $b
c = $c
}

$z = $h | ConvertTo-Json

Write-Host $z

}

A "ValueB", "ValueC"

Output:

{
"c": null,
"b": [
"ValueB",
"ValueC"
]
}

Answer 1

Hi @Joe ,

here the function works. It looks like you have to call the function a little different:

Function A {  
  PARAM ($b, $c)  
  $H = @{  
    b = $b  
    c = $c  
  }  
  $z = $h | ConvertTo-Json  
  Write-Host $z  
}  
  
# This works  
A -b ValueB -c ValueC  
# This works as well  
A ValueB ValueC  

Output looks like this in both cases:

----------

(If the reply was helpful please don't forget to upvote and/or accept as answer, thank you)

Regards
Andreas Baumgarten

Answer 2

PowerShell does not use a comma separator in a parameter list when calling PowerShell functions. Just use spaces, or use the parameter names followed by the value (e.g., A -b 'ValueB' -c 'ValueC'. OR A -c 'ValueC' -b 'ValueB')

If you use a comma you're creating a list. I.e., A "ValueB", "ValueC" creates a two element list consisting of two strings. The function "A" receives only one parameter $b (in parameter position zero), and nothing for parameter $c.

The ConvertTo-Json emits a value of "null" because the variable $c contains the value $null, and a list (or array) for variable $b.