Example of Filter to convert a ForEach

FilterExample.psm1

#Filter is just a function with the process{}
#block as the default rather than end{}. That's it, it's not scary.


# $y = 1..3
# foreach ($x in $y) {
#     "This is item $x"
# }
# #Result:
# #This is item 1
# #This is item 2
# #This is item 3

# #Easily convert it to this:
# filter 🍔 {
#     "This is item $input"
# }

filter GetJokes {
    $PSItem.Results.Joke
}

filter AddFavoriteJokePrefix {
    [CmdletBinding(SupportsShouldProcess)]
    param(
        [Parameter(Mandatory, ValueFromPipeline)][String]$Joke,
        #Person who's favorite joke it is.
        $Person = 'Steven'
    )
    if (-not $PSCmdlet.ShouldProcess($Joke, "Make it $Person's favorite")) { return }

    "$Person's favorite Joke is: $Joke"
}


function Get-DadJokes ($Person) {
    Invoke-RestMethod 'https://icanhazdadjoke.com/search' -Headers @{Accept = 'application/json' }
    | GetJokes
    | AddFavoriteJokePrefix
}


Export-ModuleMember Get-DadJokes

FilterExample.tests.ps1

Describe 'FilterExample' {
    It 'Adds Stevens name' {
        Import-Module $PSScriptRoot/FilterExample.psm1 -Force
        Get-DadJokes
        | Select-Object -First 1
        | Should -Match 'Steven'
    }
}

Describe 'GetJokes' {
    BeforeAll {
        Import-Module $PSScriptRoot/FilterExample.psm1 -Force
    }

    It 'FilterExample' {
        InModuleScope 'FilterExample' {
            [PSCustomObject]@{
                Results = @{
                    Joke = 'Pester'
                }
            }
            | GetJokes
            | Should -Be 'Pester'
        }
    }
}