Is it possible to inject a method into a service in symfony services.yml

Question

There is already plenty of documentation on the internet about injecting a service into another service like this: http://symfony.com/doc/current/components/dependency_injection/introduction.html

However, I already have a service called ObjectCache which is configured in symfony's services.yml like this:

object_cache:
  class: App\Bundle\ApiBundle\Service\ObjectCache

This service currently has two methods for getting and setting a User object. For example:

$user = new User(); // assume entity from database
$this->get('object_cache')->setUser($user);
// ...
$this->get('object_cache')->getUser(); // instance of $user

I want to create a new service which always depends on a user, so makes sense to inject the user at service creation:

class SomeService {
    public function __construct(User $user)
    {
    }
}

How would I configure services.yml such that the User is injected into my new service?

object_cache:
  class: App\Bundle\ApiBundle\Service\ObjectCache
some_service:
  class: App\Bundle\ApiBundle\Service\SomeService
  arguments: [@object_cache->getUser()????]

This didn't work, and symfony yaml documentation is sketchy to say the least.

Am I basically forced into creating a User-only flavour of the ObjectCache and injecting that into SomeService OR expecting SomeService to receive an ObjectCache and call getUser once in the constructor?

A service factory is what you are looking for: symfony.com/doc/current/components/dependency_injection/… You will end up with an injectable object_cache_user service. — Cerad
You can use the expression language like "@service('object_cache').getUser" (see symfony.com/doc/2.7/book/…). — qooplmao

teaforchris teaforchris · Accepted Answer · 2016-02-28T21:00:35

Credit to qooplmao for their comment in helping me find the answer as this is exactly what I was looking for. I thought I'd answer my own question for the benefit of others as I now have this working, plus some corrections to the syntax in the comment.

What I should have been looking for was Symfony's Expression Language which allows precisely the granularity of control I was looking for.

The resulting configuration now looks like this:

object_cache:
  class: App\Bundle\ApiBundle\Service\ObjectCache
some_service:
  class: App\Bundle\ApiBundle\Service\SomeService
  arguments: [@=service('object_cache').getUser()]

For more information on the Expression Syntax, here is some detailed documentation: http://symfony.com/doc/2.7/components/expression_language/syntax.html

(If only Symfony docs had the courtesy to provide links to such crucial information on pages that make reference to it!)

Is it possible to inject a method into a service in symfony services.yml

1 Answers