在Symfony4中将接口作为参数的Autowire类

Question

Given a class Publisher like this:

<?php

namespace App\Util\Publisher;


use Symfony\Component\Mercure\Update;
use Symfony\Component\Messenger\MessageBusInterface;

class Publisher
{

    protected $topic = null;
    protected $bus;

    /**
     * Publisher constructor.
     * @param MessageBusInterface $bus
     */
    public function __construct(MessageBusInterface $bus)
    {
        $this->topic = getenv('TOPIC_MAIN_URL');
        $this->bus = $bus;
    }

    ...

}

I would like to autowire it in my controllers like this:

/**
 * @Route("/_exp/_exp", name="exp")
 */
public function expAction(Publisher $publisher)
{
    ...
}

and I added this to my services.yaml :

Symfony\Component\Messenger\MessageBusInterface: ~

App\Util\Publisher\Publisher:
    autowire: true
    arguments: ['@Symfony\Component\Messenger\MessageBusInterface']

But I get an error:

Cannot instantiate interface Symfony\\Component\\Messenger\\MessageBusInterface

Is that related to the MessageBusInterface or am I doing something wrong with the autowiring. I followed The Symfony docs for autowiring and they seem to be the same?

Thank you!

Answer 1

I believe MessageBusInterface service is already declared by Symfony Messenger component. Try to remove Symfony\\Component\\Messenger\\MessageBusInterface: ~ from your services.yaml , otherwise you are overriding the default definition.

A note for clarification: MessageBusInterface service does not really exists, it in an alias over the "default bus" service. You can declare other buses, cf documentation