title: Best practice of Dependency Injection in Symfony2
body: <p>Before persisting an entity I need to copy and format some data in another table of my DB. I want this task to be performed as a service. 
  So I describe the service in config.yml</p>
  
  <pre><code>services:
  my_service:
      class: Acme\Bundle\AcmeBundle\DependencyInjections\MyService
      arguments: 
        entityManager: "@doctrine.orm.entity_manager"
  </code></pre>
  
  <p>I was wondering the best way to call this service. The only way I can figure out is from the controller:</p>
  
  <pre><code>$entity = new Entity($this-&gt;get('my_service'));
  </code></pre>
  
  <p>Is that the best way to proceed ? </p>