Example for using classes in PowerShell – New-Progressbar

PowerShell is a fairly easy language to learn, but to some extent, creating classes is a bit of a hidden concept. The way to do it is to wrap functions in a module and use Export-ModuleMember to make them externally visible. Here is an easy to understand example of implementing the Write-Progress cmdlet in an even easier way.

function New-Progressbar
        # Total count

        # Activity name
        [string]$ActivityName = "Running",

        # Time estimation
        [boolean]$TimeEstimationEnabled = $true

    # Create new module instance
    $m =  New-Module -ScriptBlock {
        # Internal variables
        $script:total = 1;
        $script:current = 0;
        $script:ActivityName = " ";
        $script:startTime = Get-Date;
        $script:timeEstimation = $false;
        # Functions with obvious method names
        function setActivityName($name) {$script:ActivityName = $name}
        function setTotal($tot) { $script:total = $tot}
        function getTotal($tot) { return $script:total}
        function enableTimeEstimation() {$script:timeEstimation = $true}
        function disableTimeEstimation() {$script:timeEstimation = $false}

        # Progress the progressbar one step. Optional parameter Text for defining the status message
        function Progress {
                [string]$Text = ("{0}/{1}" -f $script:current, $script:total)

            $params = @{
                Activity = $script:ActivityName
                Status = $Text
                PercentComplete = ($script:current / $script:total * 100)

            if($script:timeEstimation) {
                if($script:current -gt 5) {
                    $params["SecondsRemaining"] = (((Get-Date) - $script:startTime).TotalSeconds / $script:current) * ($script:total - $script:current)

            Write-Progress @params

            if($script:current -lt $script:total) {
                $script:current += 1
            } else {
                Write-Warning "Progressbar incremented too far"
        function Complete() {Write-Progress -Activity $script:ActivityName -Status $script:total -PercentComplete 100 -Completed}
        export-modulemember -function setTotal,getTotal,Progress,Complete,setActivityName,enableTimeEstimation,disableTimeEstimation
    } -AsCustomObject

    # Set initial values

    if($TimeEstimationEnabled) {

    return $m;

To use it, simply copy and paste the code into any PowerShell. After doing this, you have a new cmdlet available – New-Progressbar. You can use Get-Help New-ProgressBar -Full to get example usage, but here is a quick example script:

# Get a big list of files of unknown size
$files = @(dir $env:SystemRoot | select -First (Get-Random -Minimum 10 -Maximum 100))

# Create progressbar
$bar = New-Progressbar -TotalCount $files.Count -ActivityName "Processing files"

# Pretend to process files in order to progress the progressbar
$files | foreach {
    sleep -Milliseconds 100

# Complete the progressbar

As you can see, $bar is here a custom class with methods presented through the module. You can have internal methods too; only the methods exported by Export-ModuleMember is available externally.

Hope this helps someone as a quick reference to creating a PowerShell module.

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