Add Role List to FOS Userbundle Profile Edit Form

This question is similar to Symfony2: Getting the list of user roles in FormBuilder but the answers there are geared towards any form but my question is specific to a form created by the User Bundle. Problem is that the UserBundle Controller creates the form like this:

$form = $this->container->get('fos_user.profile.form');

Because of this I don't know how to send roles to my Form Type.

My answer is similar to the one by @Mihai Aurelian answered on the similar question.

Created a service called Role Helper:

<?php

namespace AppBundle\Services;

/**
 * Roles helper displays roles set in config.
 */
class RolesHelper
{
  private $rolesHierarchy;

  public function __construct($rolesHierarchy)
  {
    $this->rolesHierarchy = $rolesHierarchy;
  }

  /**
   * Return roles.
   *
   * @return array
   */
  public function getRoles()
  {
    $roles = array();

    array_walk_recursive($this->rolesHierarchy, function($val) use (&$roles) {
      $roles[] = $val;
    });

    return array_unique($roles);
  }
}

Overwrote the Form Type using Overriding Default FOSUserBundle Forms instructions and updated the default constructer to include the RolesHelper as an argument.

<?php

namespace AppBundle\Form\Type;

use Symfony\Component\Form\FormBuilderInterface;
use FOS\UserBundle\Form\Type\RegistrationFormType as BaseType;
use AppBundle\Services\RolesHelper;

class UserType extends BaseType
{
  /**
   * @var RolesHelper
   */
  private $roles;

  /**
   * @param string $class The User class name
   * @param RolesHelper $roles Array or roles.
   */
  public function __construct($class, RolesHelper $roles)
  {
    parent::__construct($class);

    $this->roles = $roles;
  }

  /**
   * {@inheritdoc}
   */
  public function buildForm(FormBuilderInterface $builder, array $options)
  {
    parent::buildForm($builder, $options);

    $builder->add('firstName')
            ->add('lastName')
            ->add('roles', 'choice', array(
              'choices' => $this->roles->getRoles(),
              'required' => false,
              'multiple'=>true
            ));
  }

  /**
   * {@inheritdoc}
   */
  public function getName()
  {
    return 'user_registration';
  }
}

Updated services.yml

app_roles_helper:
   class: AppBundle\Services\RolesHelper
   arguments: ['%security.role_hierarchy.roles%']

Added second argument to app_user.registration.form.type in services.yml:

app_user.registration.form.type:
  class: AppBundle\Form\Type\UserType
  arguments: [%fos_user.model.user.class%, @app_roles_helper]
  tags:
    - { name: form.type, alias: user_registration }