Advanced Windows PowerShell Scripting Video Training

Advanced Windows PowerShell Scripting Video Training
Advanced Windows PowerShell Scripting Video Training

Sunday, January 17, 2016

What Order do you need to list Functions?

I am actually correcting myself on this one.  I’m at 35,000 feet right now enjoying a ride in the flying tin can while looking over my notes from this past weeks Advanced PowerShell class in Fort Wayne.  One of the questions that came up is the order that you need to list functions.  I gave a bad answer. 
I had always been taught to declare a function before I call it.  It makes sense.  How do you know how to execute instructions before you are told what the instructions are?  Take a look at this code:

Function Show-A
{
    Write-Host "Function A" -ForegroundColor Green
}

Function Show-B
{
    Write-Host "Function B" -ForegroundColor Cyan
    Show-A
}

Show-B

Here I am declaring function Show-A before it is called by function Show-B.  Here is the result:
Function B
Function A

Here is my surprise.  I changed the code an placed Function Show-B1 before Function Show-A1.  I then called Function Show-B1 and it all worked.

Function Show-B1
{
    Write-Host "Function B" -ForegroundColor Cyan
    Show-A1
}
Function Show-A1
{
    Write-Host "Function A" -ForegroundColor Green
}


Show-B1

Function B
Function A

Next I insert the calling statement for function Show-B2 before Function Show-A2 is called.  In other words, I am running Show-B2 before Show-A2 is read.  It still works.

Function Show-B2
{
    Write-Host "Function B" -ForegroundColor Cyan
    Show-A2
}

Show-B2
Function Show-A2
{
    Write-Host "Function A" -ForegroundColor Green
}


Function B
Function A

One rule that I could not break is the rule on calling a variable before you declare its value.
Function Show-B2
{
    Write-Host "Function B" -ForegroundColor Cyan
    Show-A2
    Write-Host $String
}
Function Show-A2
{
    Write-Host "Function A" -ForegroundColor Green
}


Show-B2
$String = "Hello"

Here Show-B2 is attempting to write the value of $String.  The problem is, $String is not assigned until after Show-B2 is executed.  The value of $String is NULL and is not displayed.
Function B
Function A

So, I stand corrected.  I uploaded this post to the online class files that I created for this class so I could correct my error.

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