Attribute Listeners

Important Limitation

Automatic attribute discovery happens when you use EventDispatcherServiceProvider together with the Fast Forward container configuration model.

If you instantiate EventDispatcher manually, this package does not scan classes for attributes by itself.

Method-Level Attribute Example

use Symfony\Component\EventDispatcher\Attribute\AsEventListener;

final readonly class OrderConfirmed
{
    public function __construct(public string $orderNumber) {}
}

final class ReserveStockListener
{
    #[AsEventListener(priority: 100)]
    public function __invoke(OrderConfirmed $event): void
    {
        echo 'Reserving stock for ' . $event->orderNumber . PHP_EOL;
    }
}

final class NotifyOperationsListener
{
    #[AsEventListener(priority: 10)]
    public function __invoke(OrderConfirmed $event): void
    {
        echo 'Notifying operations for ' . $event->orderNumber . PHP_EOL;
    }
}

Class-Level Attributes Are Also Supported

The package inspects:

• class-level AsEventListener attributes;
• method-level AsEventListener attributes on public methods.

When the attribute does not explicitly declare an event name, the package infers the event type from the first parameter of the target method.

That means these rules must hold:

• the method must have at least one parameter;
• the first parameter must have a type declaration.

Otherwise, a FastForward\EventDispatcher\Exception\RuntimeException is raised while classifying listeners.

How Registration Works

With container integration, you place the listener class under the configuration key Psr\EventDispatcher\ListenerProviderInterface::class .

use FastForward\Config\ArrayConfig;
use FastForward\Container\ContainerInterface;
use FastForward\EventDispatcher\ServiceProvider\EventDispatcherServiceProvider;
use Psr\EventDispatcher\ListenerProviderInterface;

$config = new ArrayConfig([
    ContainerInterface::class => [
        EventDispatcherServiceProvider::class,
    ],
    ListenerProviderInterface::class => [
        ReserveStockListener::class,
        NotifyOperationsListener::class,
    ],
]);

Runtime Behavior

Attribute listeners are registered in the prioritized listener provider.

In the default service-provider composition, prioritized listeners are consulted before reflection-based listeners, subscriber-based listeners, and extra custom providers attached through configuration.

Best Practices

• Use attributes when you want the event binding to live next to the listener method.
• Keep the first parameter clearly typed.
• Prefer explicit method names for multi-method listener classes.
• Do not rely on attributes unless the service provider is part of your application bootstrap.