How do I dynamically set the type of PowerShell variables?

Question

Is it possible to get a System.Type from a string and then apply it to a variable?

The following is the function that I tried to convert to make it safer (i.e. not involve invoking a string):

Function ParseLine($Type, $VariableName, $Value){
    Invoke-Expression "[$Type] `$$VariableName = $Value"
}

I looked at New-Variable and Set-Variable, but there is no type-setting-related parameter in the definition.

I expected something that looks like below, but I couldn't find the parameter Type or equivalent:

Function ParseLine($Type, $VariableName, $Value){
    New-Variable -Name $VariableName -Value $Value -Type ([type] $Type)
}

Context: I am experimenting to create a simple parser definition that looks like:

$ResponseLogFormat = New-InputFormat {
    ParseLine -Type int -VariableName RecordLength
    RepeatedSection -RepeatCount $RecordLength {
        ParseLine string +ComputerName
        ParseLine double +AverageResponse
    }
}

$ResponseLogFormat.Parse( $FilePath )

Answer 1

You can cast variables to a specific type using the -as operator:

Function ParseLine($Type, $VariableName, $Value){
    Set-Variable $VariableName -Scope 1 -Value ($Value -as ($Type -as [type]))
}

That will use -as to create a type from the $Type string, and then use that to cast $Value.

I am not sure of your intent with the variable, but if you want to persist it after the function is finished, you need to set it in the parent scope.