If you were here Wednesday, then perhaps you already read Get the Total Parameter Count. If not, I’ll quickly tell you about it. I wanted to know how many parameters a function had whether or not those parameters were used when the function was invoked. I did this by using Get-Help against the function, from within the function. Yeah, I thought it was cleaver too, but the best part, it gave me the results I was after. If a function had three parameters, it was indicated in the function’s output. Same goes for when it had two parameters, but of course in that instance, it indicated two.

In going along with that post I had an idea. I wanted to create a way to dynamically create a function with a random number of parameters between one and ten. Then, I could prove my code was working. Sure, I could’ve used Pester, but I was after making this work — this whole, create a function with a random number of parameters thing. I needed to figure out how to get the code for a function, stored inside a variable, into an actual PowerShell function. That might’ve been confusing, but the example code in this post will probably prove helpful.

I’ll show you what I started experimenting with for discovery purposes, and then we’ll jump into the code that actually creates my function with a random number of parameters in a soon to be released second part to this post.

First, we’ll start with a here-string variable assignment. Using a here-string allows us to include multiple line breaks within our variables. As you should be able to see, the value of $FunctionCode below is the code that makes up a simple function. It includes the function keyword, a function name, an open curly brace, the function’s actual code — there’s three lines of it — and a closing curly brace, as well.

$FunctionCode = @'
Function Show-Info {
    '*****'
    'This is function Show-Info.'
    '-----'
}
'@

As expected, when I echo my variable’s value, I get back exactly what I put into it.

PS > $FunctionCode
Function Show-Info {
    '*****'
    'This is function Show-Info.'
    '-----'
}

Now, for the fun part. I’ll include all my code and then we can discuss it line by line below.

$FunctionCode = $FunctionCode -split '\n'
$FunctionCodeCount = $FunctionCode.Count - 2
$FunctionCode = $FunctionCode[1..$FunctionCodeCount]
$FunctionCode = $FunctionCode | Out-String

The first of the above four lines assigns the variable $FunctionCode the value stored in $FunctionCode after we split it on each new line. The second of the four lines creates a $FunctionCodeCount variable, assigning it the number of lines in $FunctionCode after having subtracted 2 from its value. See if you can figure why it’s two…

The third line reassigns $FunctionCode again. In this line we only return the contents of the function. This means it doesn’t return the first line of the function, which includes the function keyword, the function name, and the open curly brace. It also will not include the closing curly brace at the bottom. Our final line reassigns the $FunctionCode for a third time, taking its current value and piping that to Out-String. This will help us ensure we add back in our line breaks.

Before we create our Show-Info function, let’s take a look at the $FunctionCode variable value now.

PS > $FunctionCode
    '*****'
    'This is function Show-Info.'
    '-----'

Using Set-Item, we’ll create our function called Show-Info regardless of whether or not it already exists. That’s the difference between New-Item and Set-Item (and most New vs. Set commands). New-Item will only work if Show-Info doesn’t already exist, while Set-Item will work even if the function already exists. It if doesn’t, it’ll act like New-Item and create the function.

Set-Item -Path Function:\Show-Info -Value $FunctionCode

And finally, entering Show-Info invokes the newly created function.

PS > Show-Info
*****
This is function Show-Info.
-----

Okay, with all that out of the way, we’re going to hit the pause button. Be sure you get what’s happening here, because we’ll pick up on this post in a very soon to be released follow-up that includes the rest of what we’re after: creating a function with a random number of parameters and testing we can calculate that number correctly. If you see an area in which I can improve this, please let me know!

Before we sign off though, let me include all the above code in a single, below code block. That may end up being helpful to one of us.

Remove-Variable -Name FunctionCode,FunctionCodeCount -ErrorAction SilentlyContinue

$FunctionCode = @'
Function Show-Info {
    '*****'
    'This is function Show-Info.'
    '-----'
}
'@

$FunctionCode = $FunctionCode -split '\n'
$FunctionCodeCount = $FunctionCode.Count - 2
$FunctionCode = $FunctionCode[1..$FunctionCodeCount]
$FunctionCode = $FunctionCode | Out-String

Set-Item -Path Function:\Show-Info -Value $FunctionCode

Show-Info