When you have a PHP object which already implements Notifiers' \Symfony\Component\Notifier\Recipient\RecipientInterface interface, a notification can be sent to it directly without any further configuration. See recipients documentation for the available channel-specific interfaces which should be used.

A PHP object can be any plain PHP object, however Drupal developers may find adding recipient interfaces to entity bundle classes useful.

Bundle classes

Here we start with a pre-existing bundle class. If you have not created a bundle class yet, skip to one of variants under Creating a bundle class section below, then return to this section afterward.

Note: Bundle class implementation

This example uses the preferred BCA variant.

Note: Interface

This example implements both the Sms and Email recipient interfaces, you may choose one or many combinations, including the root RecipientInterface for channels other than Sms or Email.

WARNING

Interface methods must return a valid value. If there is a chance where the value may be empty (empty-string, NULL, FALSE, etc), then consider using a different method, via a custom event subscriber.

namespace Drupal\my_module\Entity;

use Drupal\bca\Attribute\Bundle;
use Drupal\user\Entity\User as CoreUser;
use Symfony\Component\Notifier\Recipient\EmailRecipientInterface
use Symfony\Component\Notifier\Recipient\SmsRecipientInterface

#[Bundle(entityType: 'user')]
final class User extends CoreUser implements EmailRecipientInterface, SmsRecipientInterface {
  public function getEmail(): string {
    // Email logic. E.g, from a field or complex logic.
    return 'test@example.com';
  }
  public function getPhone(): string {
    // Phone number logic. E.g, from a field or complex logic.
    return '+15551234567';
  }
}

Creating a bundle class

Simply put, a bundle class is an extension of an original entity type class, but specifically for one, or [rarely] more, bundles of the entity type. For example, you might have a Node page bundle, with its own set of specific functionality or fields. To make it easier to deal with a bundle object programmatically, in runtime or test code, you might add have a class that looks like.

namespace Drupal\my_module\Entity;

final class Page extends Node {
  public function addPageTags(...Term $tags): static {
    foreach ($tags as $tag) {
      $this->tags->appendItem($tags);
    }
    return $this;
  }
}

To use this bundle class, you need to inform Drupal of the relationship, this can be done in a few ways.

Preferably, the BCA (Bundle Class Attributes) project can be used as it's least effort and provides a great DX. Wire things together manually is also possible, just like BCA does under the hood, as described in the official changelog. There are no negative implications, like performance, from using BCA.

BCA

Take the class from above, and add the #[Bundle] attribute above the class.

namespace Drupal\my_module\Entity;

use Drupal\bca\Attribute\Bundle; 
use Drupal\node\Entity\Node;

#[Bundle(entityType: 'node', bundle: 'page')] 
final class Page extends Node {}

Ensure the module where this class lives is installed, and clear caches.

Traditional alter hooks

Drupal core 11.1, or later

namespace Drupal\my_module\Hooks;

use \Drupal\Core\Hook\Attribute\Hook;

class Hooks {
  #[Hook('entity_bundle_info_alter')]
  public function bundleAlter(array &$bundles): void {
    $bundles['node']['page']['class'] = \Drupal\my_module\Entity\Page::class;
  }
}

Ensure the module where this class lives is installed, and clear caches.

Hux

namespace Drupal\my_module\Hooks;

use \Drupal\hux\Attribute\Alter;

class Hooks {
  #[Alter('entity_bundle_info')]
  public function bundleAlter(array &$bundles): void {
    $bundles['node']['page']['class'] = \Drupal\my_module\Entity\Page::class;
  }
}

Ensure the module where this class lives is installed, and clear caches.