how to export a class in powershell v5 module

Question

I\'ve got a module setup to be like a library for a few other scripts. I can\'t figure out how to get a class declaration into the script scope calling Import-Module

Answer 1

the using statement is the way to go if it works for you. otherwise this seems to work as well.

testclass.psm1

Use a function to deliver the class

class abc{
    $testprop = 'It Worked!'
    [int]testMethod($num){return  $num * 5}
}

function new-abc(){
    return [abc]::new()
}

Export-ModuleMember -Function new-abc

someScript.ps1

Import-Module path\to\testclass.psm1
$testclass = new-abc
$testclass.testProp        # returns 'It Worked!'
$testclass.testMethod(500) # returns 2500


$testclass | gm

Name        MemberType Definition
----        ---------- ----------
Equals      Method     bool Equals(System.Object obj)
GetHashCode Method     int GetHashCode()
GetType     Method     type GetType()
testMethod  Method     int testMethod(System.Object num)
ToString    Method     string ToString()
testprop    Property   System.Object testprop {get;set;}

Answer 2

I've encountered multiple issues regarding PowerShell classes in v5 as well.

I've decided to use the following workaround for now, as this is perfectly compatible with .net and PowerShell:

Add-Type -Language CSharp -TypeDefinition @"
namespace My.Custom.Namespace {
    public class Example
    {
        public string Name { get; set; }
        public System.Management.Automation.PSCredential Credential { get; set; }
        // ...
    }
}
"@

The benefit is that you don't need a custom assembly to add a type definition, you can add the class definition inline in your PowerShell scripts or modules.

Only downside is that you will need to create a new runtime to re-load the class definition after is has been loaded for the first time (just like loading assemblies in a c#/.net domain).

Answer 3

The way I've worked around this problem is to move your custom class definition into an empty .ps1 file with the same name (like you would in Java/C#), and then load it into both the module definition and your dependent code by dot sourcing. I know this isn't great, but to me it's better than having to maintain multiple definitions of the same class across multiple files...

Answer 4

I found a way to load the classes without the need of "using module". In your MyModule.psd1 file use the line:

ScriptsToProcess = @('Class.ps1')

And then put your classes in the Class.ps1 file:

class MyClass {}

Update: Although you don't have to use "using module MyModule" with this method you still have to either:

• Run "using module MyModule"
• Or run "Import-Module MyModule"
• Or call any function in your module (so it will auto import your module on the way)

Update2: This will load the Class to the current scope so if you import the Module from within a function for example the Class will not be accessible outside of the function. Sadly the only reliable method I see is to write your Class in C# and load it with Add-Type -Language CSharp -TypeDefinition 'MyClass...'.