Service ParamConverter

config.yml

services:
    ibms.service_param_converter:
        class: Infinite\Helper\ParamConverter\ServiceParamConverter
        arguments:
            - @service_container
        tags:
            - { name: request.param_converter, converter: service, priority: 10 }

Controller.php

<?php

class CustomerController extends BaseCustomerController
{
    /**
     * Renders an appliance choice form allowing the user to
     * add an appliance if the required one doesnt exist.
     *
     * @ParamConverter("customer", converter="service", options={
     *   "service" = "ibms_customer.customer_manager",
     * })
     *
     * @param \Symfony\Component\HttpFoundation\Request $request
     * @param \Ibms\CustomerBundle\Entity\Customer      $customer
     * @return $this
     */
    public function applianceChoiceAction(Request $request, Customer $customer)
    {
      // ...
    }
}

ServiceParamConverter.php

<?php

/**
 * This file is part of the Infinite Helper Library
 *
 * (c) Infinite Networks Pty Ltd <http://www.infinite.net.au>
 *
 * For the full copyright and license information, please view the LICENSE
 * file that was distributed with this source code.
 */

namespace Infinite\Helper\ParamConverter;

use Sensio\Bundle\FrameworkExtraBundle\Configuration\ConfigurationInterface;
use Sensio\Bundle\FrameworkExtraBundle\Request\ParamConverter\ParamConverterInterface;
use Symfony\Component\DependencyInjection\ContainerInterface;
use Symfony\Component\HttpKernel\Exception\NotFoundHttpException;
use Symfony\Component\HttpFoundation\Request;

/**
 * A service aware param converter, converting request parameters
 * into objects based on service/method defined in the ParamConverter's
 * options array.
 *
 * @author Tim Nagel <t.nagel@infinite.net.au>
 */
class ServiceParamConverter implements ParamConverterInterface
{
    /**
     * @var ContainerInterface
     */
    private $container;

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

    public function apply(Request $request, ConfigurationInterface $configuration)
    {
        $options   = $this->getOptions($configuration);
        $service   = $this->container->get($options['service']);
        $arguments = $this->buildArguments($options['mapping'], $request);

        $arguments = array_filter($arguments, function ($value) {
            return !is_null($value);
        });

        if (!$arguments) {
            if (false === $configuration->isOptional()) {
                throw new NotFoundHttpException(sprintf('%s object not found.', $configuration->getName()));
            } else {
                return false;
            }
        }

        $object = call_user_func_array(array($service, $options['method']), $arguments);

        if (null === $object && false === $configuration->isOptional()) {
            throw new NotFoundHttpException(sprintf('%s object not found.', $configuration->getName()));
        }

        $request->attributes->set($configuration->getName(), $object);

        return true;
    }

    protected function buildArguments(array $mapping, Request $request)
    {
        $arguments = array();

        foreach ($mapping as $attribute) {
            $arguments[] = $request->attributes->get($attribute);
        }

        return $arguments;
    }

    public function supports(ConfigurationInterface $configuration)
    {
        $options = $this->getOptions($configuration);

        if (null === $options['service']) {
            return false;
        }

        return true;
    }

    protected function getOptions(ConfigurationInterface $configuration)
    {
        return array_replace(array(
            'mapping' => array('id'),
            'method'  => "find",
            'service' => null,
        ), $configuration->getOptions());
    }
}