Variables in modules in PowerShell

Question

I have a main script, where a few constants are defined. I then have a module (psm1) to include helper functions. The details are:

In the main script, I have imported the module as an object:

$cud2ADhleper = Import-Module -Force $cud2ADhelperModule -AsCustomObject

In the module, I have two variables,

[string]$SQLServer = $null

Function SetSQLServerAddr ([string] $name)
{
    $SQLServer = $name
}
Function GetSQLServerAddr
{
    return $SQLServer
}

My understanding is that because I am not exporting $SQLServer from the module, this variable should be local, and I should be able to Set/Get it.

It turns out otherwise. After I called SetSQLServerAddr ([string] $name), then callling GetSQLServerAddr returns $null. What did I miss?

Solution

Function SetSQLServerAddr ([string] $name)
{
    $SQLServer = $name
}

That creates a new local $SQLServer in the scope of that function.

If you want to update a variable at module (.psm1) scope then you need to prefix the name to indicate that:

Function SetSQLServerAddr ([string] $name)
{
    $script:SQLServer = $name
}

For more on scopes see get-help about_scopes.