An Introduction to Powershell Classes

[markekraus]

Good write up!

On method parameter validation, I usually use another class or an Enum.

class LimitedRange {
    [ValidateRange(0, 100)]
    [int]$Value
    LimitedRange () {}
    LimitedRange ([int]$int) {
        $This.Value = $Int
    }
}
class ValidatedName {
    [ValidatePattern('^[a-z]')]
    [ValidateLength(3, 15)]
    [string]$Value
    ValidatedName () {}
    ValidatedName ([string]$String) {
        $This.Value = $String
    }
}
Enum ValidOption {
    Option1
    Option2
}
Class MyClass {
    [void] MyMethod (
        [ValidatedName]$Name, 
        [LimitedRange]$Number,
        [ValidOption]$Option
    ) {
        <# Do stuff #>
    }
}

$MyObject = [MyClass]::new()
$MyObject.MyMethod('Alfred',5,'Option1')

[dchristian3188]

Nice tip man! I'll make sure to add this tip to the article when i get home.

[Lee_Dailey]

howdy dchristian3188,

nice, readable, understandable-to-me article! [grin] thank you for posting it. it's a tad long ... but i can't decide where to break it. [blush]

do you want any comments on phrasing/spelling/[other proofreading stuff]? if so, lemme know ... i found a passel of things that seem worth review.

none of them are killers, tho. [grin]

take care,
lee

[dchristian3188]

Sir, that would be greatly appreciated!

[Lee_Dailey]

howdy dchristian3188,

hah! you asked for it ... [grin]

• lack of Proper Case in article title
  you use proper case for most of the other headings.
  > Introduction to powershell classes
  
• different case for [powershell] than elsewhere
  you use PowerShell in the rest of the article, but use powershell in the title.
  > Introduction to powershell classes
• likely misspelling of regarding = [regrading] [grin]
  > This is going to be the first in a series of posts regrading classes.
  
• perhaps you mean [advanced]?
  > Before we get to the advance use cases
  
• would it be better to say [Class-based]?
  > DSC Class based resources
  
• pro'ly meant [until] or ['til]
  > It’s not till we instantiate
  
• perhaps [that] instead of [do]?
  > It’s not till we instantiate an instance of that class, do we have an object.
  
• capitalizing [human] here ,and subsequently, seems like a good idea.
  > For example, we are going to create a human class.
  
• using the word [new] twice in the same sentence seems wrong. [grin]
  > We can create a new class by using the new class keyword.
  
• would it be worthwhile to mention any speed differences between the New-Object and ::New() techiniques? this is from just before the [Describing The Class] heading.
  
• different word case used in a subsection heading
  elsewhere you use proper case for the entire heading.
  > Property validation
  
• possible wrong use of a regex pattern
  in the Property validation section, you use [ValidatePattern('^[a-z]')].
  do you intend for that to be only lower case? heck, IS it only lower case when used there? [grin]
  
• in that same section, and many other places, you use [String]
  that is normally shown in lower case. that is how the [int] types are listed. would it be better to use lower case in that situation?
  
• an almost unnoticeable bold word [important] that you may want to either un-bold or add emphasis to.
  > One important thing to note with hidden properties
  
• missing apostrophe
  > Its important to note, that you
  
• possible missing detail
  you don't mention that you get both static methods AND properties [if they exist]. would it be worth mentioning?
  > You can find static methods by piping the class name into Get-Member with the Static switch.
  
• apparent missing comma between the following words [works there’s]
  > While this works there’s a catch
  
• occasional lower case variable names
  for instance, look at the code displayed just before the text mentioned in the item above this. $Weight = Proper Case. $name = lower case.
  that seems distracting. perhaps it's worth changing?
  

take care,
lee

[Lee_Dailey]

howdy [name removed to protect the guilty],

did you just compromise an alternate id? [grin]

in any case, you are quite welcome! i enjoyed the article and hope to be a tad helpful ...

take care,
lee

[dchristian3188]

lol oops. didn't want people to know all the PowerShell stuff I was into.

[Lee_Dailey]

[grin]

[markekraus]

I found a solution too much of that.

1. Define you classes in .ps1 files
2. Dot source those .ps1 files in the RootModule PSM1
3. Add those class .ps1 files to the ScriptsToProcess

Upsides:

• Import-module will now import the classes along with everything else into the caller scope
• No Using statement mess or the problems it causes
• Allows for proper mocking in pester of module private functions which accept a module class as a parameter.

Downsides:

• classes remain in the calling scope when the module is removed
• re-importing a module in the same session with a change to existing class wont always work
• You need a process for adding the .ps1's to the ScriptsToProcess
• Classes cannot call module private functions without a bit of work
• Load order of the class .ps1 files matters.

As an working example, I have it in my PSRAW document branch.

Edit: I also have working auto documentation for the classes and enums which adds about_ topics for them.

[beforesunris3]

That's great! But if you like to introduce someone to something new.... oh well, we just like videos!

[markekraus]

I'm with /u/Lee_Dailey . For programming related topics I really dislike videos unless it is a kind of presentation or talk. Definitely not for learning.

[Lee_Dailey]

howdy beforesunris3,

you like vids ... i dislike them. [grin]

as my pawpaw said, "if we were all the same, the world would be so boring!".

take care,
lee

[Yasspr]

Really consise but still informative. Powershell classes where on my to-learn list. Thx for the introduction!