How do you inject dependencies in your classes from external packages?

Question

My project has external PHP packages pulled in via Composer.

I would like to inject one of the classes in that package as a dependency, instead of do new Class(); inside my Controller methods.

The documentation says you can define a service like the following:

services:
  mymodule.example_service:
    class: Drupal\path\to\Class

What do you do when you want to use an external PHP package not native to Drupal?

Answer 1

You should be able to use the fully qualified namespace for the injection:

services:
  mymodule.example_service:
    class: path\to\Class

Answer 2

If anyone want to use external packages into Drupal controller, note that you can actually use one without dependency injection. For example, if you want to use Carbon (DateTime API):

Step 1: Install the package

composer require nesbot/carbon

Step 2: Use the namespace

use Carbon\Carbon;

That's all. You are ready to use the package now.

Code sample:

<?php

namespace Drupal\foo\Controller;

use Carbon\Carbon;
use Drupal\Core\Controller\ControllerBase;

class FooController extends ControllerBase {

    public function bar() {
        return [
            '#markup' => Carbon::now(),
        ];
    }
}

?>