What am I doing wrong on PowerShell function parameters? - function

Question

I would really appreciate it if somebody could point out what I am doing wrong in passing parameters from a function back to the mainline code. I have a variable which has been successfully extracted in a function, but I cannot seem to pass that back to the mainline code
This is the code I am using:
function get-field ($field, $heading) {
$fieldPos = $script:source.AllElements.InnerText.IndexOf($heading) +1
$field = $script:source.AllElements.InnerText[$fieldPos]
# If states "Not Available", or contains a heading, process as if not found.
if ($field -eq "Not Available ") {$fieldPos = 0}
if ($field -eq $heading) {$fieldPos = 0}
# Check that a valid entry was received
if ($fieldPos -eq 0) {
Write-Host "Warning:" $heading "was not found"
} else {
$field = $field.Trim()
}
return $field
}
get-field $email "Name"
get-field $address "Address"
I have verified that within the function, the $field and $heading parameters contain the correct information, so why aren't the $email and $address fields being populated?

Answer 1

You're not doing it totally wrong.
Have a look at this example:
function get-field ($field, $heading) {
return "$field - $heading"
}
$address = get-field "AddressFiled" "AddressHeading"
$address
to catch the returned value in a variable for further use, you should call the function like in the above example.

Answer 2

Parameters in PowerShell are normally used for passing values into a function. The output of a function must be assigned to a variable in the statement that invokes the function. Also, it's bad design to use global variables inside a function, because that makes debugging significantly more difficult.
Your code should look somewhat like this:
function Get-Field ($data, $heading) {
$fieldPos = $data.IndexOf($heading) + 1
$field = $data[$fieldPos].Trim()
# If states "Not Available", or contains a heading, process as if not found.
if ($field -eq 'Not Available' -or $field -eq $heading) {
Write-Host "Warning: ${heading} was not found"
}
$field
}
$email = Get-Field $script:source.AllElements.InnerText 'Name'
$address = Get-Field $script:source.AllElements.InnerText 'Address'
You can have out parameters if you want to, but they're rather uncommon in PowerShell, probably because they're not as straight-forward to use as one would like.
function Get-Field ([ref]$field, $data, $heading) {
$fieldPos = $data.IndexOf($heading) + 1
$field.Value = $data[$fieldPos].Trim()
# If states "Not Available", or contains a heading, process as if not found.
if ($field -eq 'Not Available' -or $field -eq $heading) {
Write-Host "Warning: ${heading} was not found"
}
}
$email = $null
Get-Field ([ref]$email) $script:source.AllElements.InnerText 'Name'
$address = $null
Get-Field ([ref]$address) $script:source.AllElements.InnerText 'Address'