How do you properly create objects with functions in Powershell? - powershell

Question

We have a Powershell script which loads some configuration for our application from a json file via something like:
$ourApplicationSettings=Get-Content -Raw -Path $EnvironmentFile | ConvertFrom-Json
Now that I have an object which contains all of the settings, I'd like to create a handful of functions which can operate on either the $settings object directly, or some portion of it.
The best practices articles I've read for Powershell state that functions should be of the form: Verb-Noun, which sounds like developers would be expected to write functions like:
Get-OurAppSourceDirectory $ourApplicationSettings
DoSomething-OurApp $ourApplicationSettings
This seems very counter intuitive as it means that there is no way to easily find all of the functions associated with OurApp.
One article proposes one possible way would be to use a function like:
function New-OurAppConfig {
$appConfig = Get-Content -Raw -Path $EnvironmentFile | ConvertFrom-Json
$appConfig
}
but this way I'm not sure how to add member functions so that I could write:
$config = New-OurAppConfig
$config.Get-SrcDirectory
$config.Invoke-ActionABC

Answer 1

Well, you can search for that. Get-Command *ourapp*. So that one is not true. As for the second question:
$config = New-OutAppConfig
$var = Get-SrcDirectory $config
Invoke-ActionABC $var
or alternatively you can do a meta function that calls all those functions, so you could just call it once and thats it.
Also, it seems like what you are trying to achieve can be done with classes in PowerShell. https://blogs.technet.microsoft.com/heyscriptingguy/2015/09/04/adding-methods-to-a-powershell-5-class/

Answer 2

You can use Add-Member to add script methods to an existing object:
$foo = '{"value":23}' | ConvertFrom-Json
$foo | Add-Member -Type ScriptMethod -Name Multiply -Value {
Param($factor)
$this.value * $factor
}
$foo.Multiply(2) # output: 46
$foo.Multiply(3) # output: 69
That approach is a little awkward, though, both because PowerShell prior to v5 wasn't really built for full OO and because calling methods on a configuration object feels odd.
Generally it's more PoSh to read your configuration once at the beginning of your script and then either use it as a global singleton:
$cfg = Get-Content 'C:\path\to\your.json' -Raw | ConvertFrom-Json
function Get-Something {
...
Invoke-Other $cfg.Whatever
...
}
Get-Something
or make the configuration a mandatory parameter for your functions:
$cfg = Get-Content 'C:\path\to\your.json' -Raw | ConvertFrom-Json
function Get-Something {
Param(
[Parameter(Mandatory=$true)
$Config
)
...
Invoke-Other $Config.Whatever
...
}
Get-Something -Config $cfg