Question concerning Method in new Type/Class

PowerShell Help
1

Hello, this is my first post and I hope it is in the right category.

When I create a new Type with own constructor and method like:

class MyClass
{
[string]$name
[datetime]$startdate
[int]$id

MyClass([string]$name, [datetime]$startdate,[int]$id)
{
$this.name = $name
$this.startdate = $startdate
$this.id = $id
}
[timespan]GetPeriod()
{
$today = Get-Date
$period = $today - $this.startdate
return $period
}
}

And I then look at the methods with:

[MyClass] | Get-Member -MemberType *

The method “GetPeriod” does not appear. What do I miss - does anyone have an idea?

Thank you.

2

Hi, welcome to the forum :wave:

You don’t actually have a class yet, just a definition of a class.

You’re actually just piping your class definition to Get-Member and the output you’re seeing is the members of an instance of the System.RuntimeType class.

PS E:\Temp\Files> [MyClass] | Get-Member         
    TypeName: System.RuntimeType

To see the members of your class, first create an instance of it:

$instance = New-Object -TypeName MyClass -ArgumentList 'myFirstClass',(Get-Date),1
$instance | Get-Member

et voila:

   TypeName: MyClass

Name        MemberType Definition
----        ---------- ----------
Equals      Method     bool Equals(System.Object obj)
GetHashCode Method     int GetHashCode()
GetPeriod   Method     timespan GetPeriod()
GetType     Method     type GetType()
ToString    Method     string ToString()
id          Property   int id {get;set;}
name        Property   string name {get;set;}
startdate   Property   datetime startdate {get;set;}
1 Like
3

A couple of additional notes.

If you create a custom constructor, consider adding a parameterless constructor to create instance with no arguments.

You can use the static modifier for properties/methods that aren’t instance specific. The GetPeriod() method is a bad example but just for reference.

class MyClass{
    [string]$name
    [datetime]$startdate
    [int]$id

    MyClass(){}

    MyClass([string]$name, [datetime]$startdate,[int]$id){
        $this.name = $name
        $this.startdate = $startdate
        $this.id = $id
    }

    [timespan]GetPeriod(){
        $today = Get-Date
        $period = $today - $this.startdate
        return $period
    }

    static [timespan]GetPeriod($obj){
        $today = Get-Date
        $period = $today - $obj.startdate
        return $period
    }
}

Now you can use either of these to achieve the same result.

$instance = [MyClass]::new('Name',(Get-Date),123)
$instance.GetPeriod()

$instance = [MyClass]::new()
$instance.Name = 'Name'
$instance.StartDate = Get-Date
$instance.Id = 123
[myclass]::GetPeriod($instance)
2 Likes
4

Thank you very much for the answers. It works. Creating an actual instance let’s the method show up in Get-Member. I hadn’t even thought of that. It had assumed that Get-Member checks the definition, the recipe so to say.
I still wonder: When I pipe for example [DateTime] to Get-Member:

[DateTime] | Get-Member

ist shows me the methods of [DateTime]. When I do the same with [MyClass] it shows me quite a few methods as well just not the method GetPeriod that I had created in the class. Does someone have any idea why that is?

5

Did you miss the part about static members? Those are members of the class, where non static are members of the instantiation of the class.