EntityExample

entity.php

<?php
class User
{
}

class ActivityGroup
{
}

interface UserFactory
{
    public function create($email);
}

interface ActivityGroupFactory
{
    public function create($name, $description);
}

class SymfonyUserFactory implements UserFactory, ContainerAware
{
    protected $container;

    public function setContainer(Container $container)
    {
        $this->container = $container;
    }

    public function create($email)
    {
        $this->container->enterScope('UserBundle:entities:user');
        $this->container->setParameter('UserBundle:entities:user.email', $email);
        $entity = $this->container->get('UserBundle:entities.user');
        $this->container->leaveScope('UserBundle:entities:user');
        return $entity;
    }
}

class SymfonyActivityGroupFactory implements ActivityGroupFactory
{
    public function create($name, User $moderator)
    {
        return new ActivityGroup($name, $moderator);
    }
}

class ActivityGroupController
{
    private $userFactory;
    private $userRepository;
    private $activityGroupFactory;

    private $em;

    public function post()
    {
        $moderator = $this->userRepository->findByEmail(...);
        if (!$moderator) {
            $moderator = $this->userFactory->create(...);
        }

        $activityGroup = $this->activityGroupFactory->create('My funky activity group', $moderator);
    }
}