Function

Parameter

Parameters are wrapped inside a function block with param(...)

function Foo {
    param (
        $Foo
    )
}

NOTE

Default type of a parameter is System.Object.

Positional Parameter

Positional parameters allows passing values with explicit names.

function Foo {
    param (
        [string] $Foo,
        [string] $Bar
    )
    
    Write-Output "$Foo $Bar"
}

Foo -Foo foo -Bar bar
Foo foo bar # it's the same

Default Parameter

function Foo {
    param (
        [string]$foo = "foo"
    )
}

Flags

Defining flags that represents a toggle needs a special type called switch. switch has the same nature of bool, but bool parameter requires explicit assignment when the function being called. While switch will remain $false when unspecified.

function Foo {
    param (
        [switch]$Foo
        [bool]$Bar
    )
}

# this is why we should use `switch` instead.
Foo -Foo -Bar $true

Required Parameter

All parameters are optional by default. Use [Parameter(Mandatory=$true)] to mark it as required.

param (
    [Parameter(Mandatory=$true)]
    [string]$RequiredName
)

Parameter Alias

Parameters can have aliases. It's not needed for most of time though since pwsh can distinguish option by leading string.

function Person {
    param (
        [Alias("n")] 
        [string]$Name,

        [Alias("a")] 
        [int]$Age
    )
    Write-Host "Name: $Name, Age: $Age"
}

Person -n "Alice" -a 30

Lifetime

• Function should be define before it was called.