Objects made easy

Ok, so you've noticed me struggle.
But that's how you learn.

In my last post I was trying to simplify the creation of objects in various way but I forgot about the golden rule, KISS (Keep It Simple, Stupid).

That is, if it looks complex, write a function...

So the only way to create an object in PowerShell v2 with ordered properties is like this, right?

$Kalle = New-Object PSObject
$Kalle| Add-Member -MemberType NoteProperty -Name First -Value "Kalle"
$Kalle| Add-Member -MemberType NoteProperty -Name Last -Value "Svensson"
$Kalle| Add-Member -MemberType NoteProperty -Name Phone -Value "555-55 55 55"
$Kalle

First               Last                    Phone
-----               ----                    -----
Kalle               Svensson                555-55 55 55 

So lets make it a an advanced function.

function New-CustomObject
    {
    param (
        [array]$PropertyArray
    )

    $Object = New-Object PSObject
   
    foreach ($Property in $PropertyArray){
        $Object | Add-Member -MemberType 'NoteProperty' -Name $Property -Value $null
    }
   
    return $Object
}

Then putting the new function to use

$Kalle = New-CustomObject -PropertyArray "First","Last","Phone"

$Kalle.First = "Kalle"
$Kalle.Last = "Svensson"
$Kalle.Phone = "555 - 55 55 55"

$Kalle

First               Last                    Phone
-----               ----                    -----
Kalle               Svensson                555-55 55 55 

And I'm done

Finally, objects is making sence

I've been struggling with one last part of MS PowerShell for a while now, namely the internal data structures of PowerShell objects (and all .Net objects for that matter).

They are neat, but how do I define custom outputs in an easy way to read in my script code?

You've all read about Add-Member -type and New-Object System.Object.
They do work, but they are a pig to write.

Now, you might say "But why don't simply use hash tables?".
Well, they can't be ordered in PowerShell v2. You'll need PowerShell v3 to build it, i.e.

[ordered]@{First = "Sven"; Last = "Karlsson"}

and then there's the matter of hash tables only containing two values (key and value) which makes the construct confusing :/

Say I want to output a phone list as an object in PowerShell.

$propertyhashSven = @{}
$propertyhashSven.first = "Sven"
$propertyhashSven.last = "Karlsson"
$propertyhashSven.phone = "040-11 12 13"

> $propertyhashSven

Name                           Value
----                           -----
last                           Karlsson
phone                          040-11 12 13
first                          Sven

> $sven = New-Object PSObject -Property $propertyhashSven

> $sven

last                      phone                       first
----                      -----                       -----
Karlsson                  040-11 12 13                Sven

The properties is not ordered at ALL :/

But how about this...

First thing is to define the object. The easiest way I found is to first create my own data type in C#.

add-type @"
 public struct contact {
    public string First;
    public string Last;
    public string Phone;
 }
"@

Then, simply create the objects using that data type.

> $sven = New-Object contact
> $kalle = New-Object contact

And then populate it with some properties

> $sven.First = "Sven"
> $sven.Last = "Karlsson"
> $sven.Phone = "040-11 12 13"

> $kalle.first = "Kalle"
> $kalle.last = "Svensson"
> $kalle.phone = "08-555 555"

And then finally wrapping it up in a phone book as an array.

> $phonebook = @($sven,$kalle)

And there you go :)

> $phonebook

First                     Last                        Phone
-----                     ----                        -----
Sven                      Karlsson                    040-11 12 13
Kalle                     Svensson                    08-555 555

Want to sort it by first name? No problems.

> $phonebook | Sort-Object First

First                     Last                       Phone
-----                     ----                       -----
Kalle                     Svensson                   08-555 555
Sven                      Karlsson                   040-11 12 13

And adding more entries is just a matter of expanding the array...

> $sture = New-Object contact
> $sture.first = "Sture"

> $phonebook = $phonebook + $sture 

> $phonebook

First                     Last                       Phone
-----                     ----                       -----
Sven                      Karlsson                   040-11 12 13
Kalle                     Svensson                   08-555 555
Sture

And hopefully, it won't break anything ;)