How to Work with Services Provided by Third-Party Bundles

Since Symfony and all third-party bundles configure and retrieve their services via the container, you can easily access them or even use them in your own services. To keep things simple, Symfony by default does not require that controllers must be defined as services. Furthermore, Symfony injects the entire service container into your controller. For example, to handle the storage of information on a user's session, Symfony provides a session service, which you can access inside a standard controller as follows:

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public function indexAction($bar)
{
    $session = $this->get('session');
    $session->set('foo', $bar);

    // ...
}

In Symfony, you'll constantly use services provided by the Symfony core or other third-party bundles to perform tasks such as rendering templates (templating), sending emails (mailer), or accessing information on the request through the request stack (request_stack).

You can take this a step further by using these services inside services that you've created for your application. Beginning by modifying the NewsletterManager to use the real Symfony mailer service (instead of the pretend app.mailer). Also pass the templating engine service to the NewsletterManager so that it can generate the email content via a template:

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// src/AppBundle/Newsletter/NewsletterManager.php
namespace AppBundle\Newsletter;

use Symfony\Component\Templating\EngineInterface;

class NewsletterManager
{
    protected $mailer;

    protected $templating;

    public function __construct(
        \Swift_Mailer $mailer,
        EngineInterface $templating
    ) {
        $this->mailer = $mailer;
        $this->templating = $templating;
    }

    // ...
}

Configuring the service container is easy:

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# app/config/services.yml
services:
    app.newsletter_manager:
        class:     AppBundle\Newsletter\NewsletterManager
        arguments: ['@mailer', '@templating']

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<!-- app/config/services.xml -->
<?xml version="1.0" encoding="UTF-8" ?>
<container xmlns="http://symfony.com/schema/dic/services"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://symfony.com/schema/dic/services
        http://symfony.com/schema/dic/services/services-1.0.xsd">

    <service id="app.newsletter_manager" class="AppBundle\Newsletter\NewsletterManager">
        <argument type="service" id="mailer"/>
        <argument type="service" id="templating"/>
    </service>
</container>

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// app/config/services.php
use AppBundle\Newsletter\NewsletterManager;

$container->register('app.newsletter_manager', NewsletterManager::class)
    ->setArguments(array(
        new Reference('mailer'),
        new Reference('templating'),
    ));

The app.newsletter_manager service now has access to the core mailer and templating services. This is a common way to create services specific to your application that leverage the power of different services within the framework.