Using Functions in Button Actions

[kendallmoreland]

Hello,

I've been playing around with PoshUI and as far as I can tell from using it and the documentation I've read is that in a button action, I cannot use functions that are defined outside of the action. Is there anyway to get around this or a way to import functions into the action?

[freddysae0]

Right, functions from your script aren't visible inside an action. The reason determines the workarounds:

• -Action is stored as text. Add-UICanvasControlInternal.ps1 does $ctrl.Action = $Action.ToString().Trim().
• When you click, the engine runs that text in its own runspace (CanvasBridge.cs: RunspaceFactory.CreateRunspace(), then ps.AddScript(script) for each action). Your authoring session (its functions and variables) isn't there, and $PSScriptRoot is empty.
• That runspace is reused for every action. Anything an action defines (functions, imported modules) is still there for later actions.

So any of these work. I checked each by reproducing the same pipeline (one reused runspace, actions passed as ToString() text, run with AddScript):

1. Dot-source a helpers file (or Import-Module) inside the action

Add-UICanvasButton 'Run' -Action {
    . 'C:\Tools\MyApp\helpers.ps1'        # absolute path: $PSScriptRoot is empty here
    Get-Greeting 'button A'
}

After the first action has loaded it, other actions can call Get-Greeting without loading it again. Still, loading it in every action that needs it is safer, since you can't control which button is clicked first. Import-Module MyHelpers works the same way if the module is on PSModulePath.

2. Insert the path at authoring time. Since the action is just text, build it with [scriptblock]::Create so the real path ends up in it:

$helpers = Join-Path $PSScriptRoot 'helpers.ps1'
Add-UICanvasButton 'Run' -Action ([scriptblock]::Create(". '$helpers'; Get-Greeting 'button A'"))

3. Copy functions you already defined in your script into the action:

function Get-Thing { param($x) "thing: $x" }
function Format-Thing { param($t) "[$t]" }

$defs = foreach ($n in 'Get-Thing','Format-Thing') {
    "function $n {`n$((Get-Item "function:$n").ScriptBlock)`n}"
}
Add-UICanvasButton 'Run' -Action ([scriptblock]::Create(
    ($defs -join "`n") + "`n" + 'Show-UICanvasToast (Format-Thing (Get-Thing "clicked"))'
))

This keeps everything in one script file, with no external helpers file.

Note that variables from your script aren't available inside actions either, for the same reason. To pass data, use reactive state (New-UICanvasState at authoring time, Get-UICanvasState in the action) or put the values into the text as in option 2.