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In PowerShell, a scripting language commonly used for task automation and configuration management, the concept of noninstantiability is similar to that in object-oriented programming languages. Although PowerShell is primarily a scripting language, it supports object-oriented features, including classes. In some scenarios, you might want to create utility classes that should not be instantiated directly. Enforcing noninstantiability in PowerShell involves making the class constructor private, ensuring that instances of the class cannot be created directly by users.

Enforcing noninstantiability in PowerShell offers several key advantages: 1. **Prevents Misuse**: By preventing the instantiation of a class that is not intended to be instantiated, you avoid unintended behaviors or logical errors in your scripts. 2. **Encapsulates Implementation Details**: A private constructor allows you to encapsulate the internal logic of the class, ensuring that only the intended API is exposed to users. 3. **Encourages Proper Design**: This approach encourages the use of static methods and properties, which can lead to more maintainable and clear code.

In PowerShell, you can enforce noninstantiability by defining a class with a private constructor, ensuring that the class cannot be instantiated directly:

```powershell class UtilityClass {

   # Private constructor to prevent instantiation
   UtilityClass() {
       throw [System.NotImplementedException]::new("This class cannot be instantiated.")
   }

   # Static method to provide utility functionality
   static [void] UtilityMethod() {
       Write-Output "This is a utility method."
   }

1. Usage

[UtilityClass]::UtilityMethod() # Works fine

try {

   $obj = [UtilityClass]::new()  # Throws an error

   Write-Output $_.Exception.Message  # Outputs: "This class cannot be instantiated."

In this example, the `UtilityClass` has a private constructor that throws an exception if an attempt is made to instantiate the class. The `UtilityMethod` is a static method that provides the intended functionality without requiring instantiation.

In PowerShell, you can also define a class with only static members and a private constructor to enforce noninstantiability:

```powershell class MathUtils {

   # Private constructor to prevent instantiation
   MathUtils() {}

   # Static utility methods
   static [int] Add([int]$a, [int]$b) {
       return $a + $b
   }

   static [int] Subtract([int]$a, [int]$b) {
       return $a - $b
   }

1. Usage

Write-Output ([MathUtils]::Add(10, 5)) # Outputs: 15 Write-Output ([MathUtils]::Subtract(10, 5)) # Outputs: 5

1. Uncommenting the following line will result in an error
2. $mathUtils = [MathUtils]::new() # Throws an error

```

In this example, the `MathUtils` class is designed to be used statically, and its private constructor ensures that the class cannot be instantiated.

In cases where you need a single instance of a class, you can use a singleton pattern with a private constructor:

```powershell class Singleton {

   static [Singleton] $Instance

   # Private constructor to prevent instantiation
   Singleton() {}

   static [Singleton] GetInstance() {
       if (-not [Singleton]::Instance) {
           [Singleton]::Instance = [Singleton]::new()
       }
       return [Singleton]::Instance
   }

   [void] DoSomething() {
       Write-Output "Singleton instance is doing something!"
   }

1. Usage

$singleton = [Singleton]::GetInstance() $singleton.DoSomething() # Outputs: Singleton instance is doing something!

try {

   $anotherSingleton = [Singleton]::new()  # Throws an error

   Write-Output $_.Exception.Message  # Outputs: "Cannot find an overload for 'new' and the argument count: '0'."

In this example, the `Singleton` class has a private constructor and a static `GetInstance` method that returns the single instance of the class. This ensures that only one instance of the class can exist.

Another approach to enforce noninstantiability is by using a module to encapsulate functions, effectively preventing the need for class instantiation:

```powershell

1. UtilityModule.psm1

function Add-Utility {

   param([int]$a, [int]$b)
   return $a + $b

function Subtract-Utility {

   param([int]$a, [int]$b)
   return $a - $b

Export-ModuleMember -Function Add-Utility, Subtract-Utility ```

```powershell

1. Usage

Import-Module -Name ./UtilityModule.psm1

Write-Output (Add-Utility -a 10 -b 5) # Outputs: 15 Write-Output (Subtract-Utility -a 10 -b 5) # Outputs: 5 ```

In this example, the functions `Add-Utility` and `Subtract-Utility` are encapsulated within a module. This design pattern eliminates the need for class instantiation and provides a clean API.

Enforcing noninstantiability in PowerShell is useful in the following scenarios: - **Utility Classes**: When creating a class that contains only static methods or properties and is not meant to be instantiated. - **Singleton-Like Classes**: When you want to ensure that a class is never instantiated directly but can still be accessed in a controlled manner through a static method. - **Module Design**: When designing modules that contain utility functions, enforcing noninstantiability can prevent misuse and clarify the intended usage. - **API Design**: When developing a PowerShell module or script where certain classes should not be instantiated by users, enforcing noninstantiability can prevent misuse and maintain the integrity of the API.

In PowerShell, enforcing noninstantiability with a private constructor is a best practice when you want to prevent a class from being instantiated. This technique is particularly useful for utility classes, singleton patterns, and scenarios where class instances would lead to logical errors or misuse. By enforcing noninstantiability, you can write more maintainable, clear, and reliable code, especially in situations where class instances should be tightly controlled.

For more information on enforcing noninstantiability in PowerShell, consider exploring the following resources:

• https://docs.microsoft.com/en-us/powershell/scripting/learn/deep-dives/everything-about-classes
• https://docs.microsoft.com/en-us/powershell/scripting/developer/module/writing-a-windows-powershell-module
• https://docs.microsoft.com/en-us/powershell/scripting/learn/deep-dives/everything-about-objects

These resources provide additional insights and best practices for using noninstantiability effectively in PowerShell.