💡 Today I Learned

Parameters: general guide

In powershell, parameters -- you know, arguments -- can be written in a lot of ways.

Even a script that declares no parameters can access the parameters that are handed to it.

As can a function, a named cmdLet, etc.

You can declare parameter names without specifying a type, e.g.

function New-Satelitte ($sateliteName, $weightInGrams) {
	write-host "The $sateliteName will weigh $weightInGrams" -f Yellow;
}

...and a trap for young players, having just written such a function...

You call it WITHOUT parentheses.

You call it like this:

New-Satelitte "The Nazgul Banana" 500

and NOT like this:

New-Satelitte ("The Nazgul Banana", 500)   # NO! Not like this!

...as that would be interpreted as you sending a single parameter, an array with two values

("The Nazgul Banana", 500).GetType()

IsPublic IsSerial Name                                     BaseType
-------- -------- ----                                     --------
True     True     Object[]                                 System.Array

Hence $SatelliteName would be an array of objects.

Apart from remembering the "no brackets" syntax -- you also need to learn how to give types to your parameters, and so much more.

param()

Function Invoke-Clippy{
param(
		$text="Hi! I am Clippy, your office assitant. Would you like some assistance today?"
)

	write-host $text -foregroundColor yellow;
}

[string]

param (
    [string]$text
)

[Parameter()]

param (
    [Parameter(Mandatory)]
    $ApiKey
)

[ValidateNotNullOrEmpty()]

param (
    [Parameter(Mandatory)]
    [ValidateNotNullOrEmpty()]
    [string]$ApiKey
)

todo: ValueFromPipeline

[ValueFromPipelineByPropertyName()]

function kvi {

AAA reads stream. you give it an object. it will iterate it and return an object which is the keys.

[CmdletBinding()] Param( [Parameter(ValueFromPipelineByPropertyName)]$Keys, [Parameter(ValueFromPipelineByPropertyName)]$Value )

param (
    [Parameter(Mandatory)]
    [ValidateNotNullOrEmpty()]
    [string]$ApiKey
)

todo: ValueFromPipelineByPropertyName todo: ParameterSetName todo: PSAvoidUsingPositionalParameters todo: ValueFromRemainingArguments / Passthrough

Source(s)

See also