Create a singleton object with dependency injection in Magento

We know how to create objects with Object Manager, and we also know that it is frowned upon in Magento land. Instead of using Object Manager, we’ll create instances of objects with dependency injection instead.

This is easier than you think, especially since the introduction of promoted properties in PHP 8. Our first step is to create a constructor. In PHP, we’ll do this by creating a public function named __construct:

Here’s how the controller looks after adding an empty constructor:

<?php

declare(strict_types=1);

nam...