Interface-based DI configuration in Symfony - php

Question

In my Symfony project I'll have lot of classes that have similar dependecies (however, the classes are not directly related to each other). For example, most of them requires access to EventBus.
In other framework I was able to specify an interface for the class, for example:
interface EventBusAwareInterface
{
public setEventBus(EventBus $bus);
public getEventBus() : EventBus
}
and then configure DI container to recognize such objects that implements this interface, and call their setEventBus() method with proper argument.
I wonder if there's a method to do the same in Symfony4.

Answer 1

You can use _instanceof directive in your services.yaml like that:
services:
_instanceof:
App\EventBusAwareInterface:
calls:
- method: setEventBus
arguments:
- '#event.bus.service'

Answer 2

My original comment was not quire correct. You can use #inject but it seems to require an additional jms bundle. Could have sworn the container supported it out of the box but I guess not.
However, autowire supports a #required annotation which seems to do the trick.
use Symfony\Component\HttpFoundation\RedirectResponse;
use Symfony\Component\Routing\Generator\UrlGeneratorInterface;
use Symfony\Component\Routing\RouterInterface;
trait RouterTrait
{
/** #var RouterInterface */
protected $router;
/**
* #param RouterInterface $router
* #required
*/
public function setRouter(RouterInterface $router)
{
$this->router = $router;
}
// Copied directly from Symfony ControllerTrait
protected function generateUrl(
string $route,
array $parameters = array(),
int $referenceType = UrlGeneratorInterface::ABSOLUTE_PATH): string
{
return $this->router->generate($route, $parameters, $referenceType);
}
protected function redirect($url, $status = 302) : RedirectResponse
{
return new RedirectResponse($url, $status);
}
protected function redirectToRoute($route, array $parameters = array(), $status = 302) : RedirectResponse
{
return $this->redirect($this->generateUrl($route, $parameters), $status);
}
}
Now, any autowired service that uses the RouterTrait will automatically get the router injected.

Answer 3

Yes, something even simpler is very possible. However, I would not encourage over-usage as it can very quickly introduce things like method name collisions and reduce code readability.
That said, Symfony introduced service auto-wiring concept starting with 3.3 (I think), which can be used to have dependency injection with zero-config. In PHP, interfaces cannot contain implementation, but, traits can. So, you could do something like this:
trait FooTraitHandler
{
/**
* #var LoggerInterface
*/
private $logger;
public function __construct(LoggerInterface $logger)
{
$this->logger = $logger;
}
}
And then:
class RealService
{
use FooTraitHandler;
public function multiply($a, $b)
{
$this->logger->log(LogLevel::ALERT, "Doing some basic math!");
return $a * $b;
}
}
And finally, for example, your controller could inject this RealService service and use multiply method as usual.
So, couple of things worth mentioning:
You do not need pair of getter/setter - trait's member is visible in class utilizing it.
You can utilize many traits, achieving just what you wanted with many interfaces
Finally, if some of utilized traits have methods with same name, you'll get a fatal error. As per official docs:
If two Traits insert a method with the same name, a fatal error is produced, if the conflict is not explicitly resolved. To resolve naming conflicts between Traits used in the same class, the insteadof operator needs to be used to choose exactly one of the conflicting methods.
But, in my opinion, doing so deteriorates code readability substantially.
Hope this helps...