How does Symfony injects its DI Container inside every class that extends the Controller one?

Question

for someone it might seem stupid, anyway I am new to the Symfony world and reading the documentation I came up with a doubt:

How does Symfony inject the DI Container instance inside of each Controller class which extends Controller in such a way that you can easily access a service from the container using the get($id) method??? Like here:

use Acme\HelloBundle\Newsletter\NewsletterManager;

// ...

public function sendNewsletterAction()
{
    $mailer = $this->get('my_mailer');
    $newsletter = new NewsletterManager($mailer);
    // ...
}

I saw the source of the Controller class from GitHub, the Controller class in Symfony extends the abstract class ContainerAware which implements the ContainerAwareInterface interface, which has a method setContainer(ContainerInterface $container = null);

I can assume that the Controller itself attempts to set a reference to the Container instance calling setContainer inherited from the ContainerAware abstract class, but I am not sure whether I am right or not, but since I know that in Symfony2 every service (object with particular functionality) is under the supervision of the DI Container, who is responsible to inject the container to the Controller setContainer() setter? The Container itself? But how?

Thanks for the attention!

jrdn jrdn · Accepted Answer · 2014-07-23T11:01:36

With controllers, Symfony2 uses the ControllerResolver class to determine if the Controller is an implementation of ContainerAwareInterface, and will inject the container that way. See this file (lines highlighted):

https://github.com/symfony/symfony/blob/master/src/Symfony/Bundle/FrameworkBundle/Controller/ControllerResolver.php#L79-L82

As for other services, you will have to manually inject the container into them via service definitions.

How does Symfony injects its DI Container inside every class that extends the Controller one?

1 Answers