Symfony 4: Trait + Setter injection

SerializerAware.php

<?php declare(strict_types = 1);

namespace App\Core\DependencyInjection\Extension;

use App\Core\Service\Serializer;

/**
 * Extends the class with awareness of Serializer service
 *
 * Created for free for the anarchist movement around the world.
 *   See iwa-ait.org, zsp.net.pl, wolnosciowiec.net
 */
trait SerializerAware
{
    /**
     * @var Serializer $serializer
     */
    protected $serializer;

    /**
     * Setter injector (for the container usage)
     *
     * @param Serializer $serializer
     */
    public function setSerializer(Serializer $serializer)
    {
        if ($this->serializer instanceof Serializer) {
            return;
        }

        $this->serializer = $serializer;
    }

    protected function getSerializer(): Serializer
    {
        return $this->serializer;
    }
}

SerializerInjectionPass.php

<?php declare(strict_types = 1);

namespace App\Core\DependencyInjection\Compiler;

use App\Core\DependencyInjection\Extension\SerializerAware;
use App\Core\Service\Serializer;
use Symfony\Component\DependencyInjection\{ContainerBuilder, Reference};
use Symfony\Component\DependencyInjection\Compiler\CompilerPassInterface;

/**
 * Inject Serializer service in every class where a trait "SerializerAware" is used
 * (uses setter injection)
 *
 * Created for free for the anarchist movement around the world.
 *   See iwa-ait.org, zsp.net.pl, wolnosciowiec.net
 */
class SerializerInjectionPass implements CompilerPassInterface
{
    public function process(ContainerBuilder $container)
    {
        foreach ($container->getDefinitions() as $definition) {
            if (is_subclass_of($definition->getClass(), SerializerAware::class)) {
                $definition->addMethodCall('setSerializer', new Reference(Serializer::class));
            }
        }
    }
}