Stoppable Events

Convenience Helpers

The package provides:

• FastForward\EventDispatcher\Event\Event
• FastForward\EventDispatcher\Event\StoppableEventTrait

Both store propagation state for you.

The Important Detail

Event extends Symfony's base event class and keeps its public stopPropagation() API.

StoppableEventTrait exposes the same public method, which means listeners can call it directly too.

Recommended Pattern

use FastForward\EventDispatcher\Event\Event;

final class UserDeletionRequested extends Event
{
    public function __construct(public readonly int $userId) {}
}

final class PreventAdminDeletionListener
{
    public function __invoke(UserDeletionRequested $event): void
    {
        if ($event->userId === 1) {
            $event->stopPropagation();
        }
    }
}

How the Dispatcher Treats Stoppable Events

• If the event is already stopped before dispatch starts, the dispatcher returns immediately.
• After each listener call, the dispatcher checks whether propagation has been stopped.
• If the event is later wrapped in NamedEvent , the wrapper mirrors the stoppable state of the original event.

What This Is Good For

Stoppable events are a good fit for:

• validation pipelines;
• veto rules;
• security checks;
• first-match workflows where later listeners should not run.

What It Does Not Do

Stopping propagation does not undo work already done by earlier listeners. It only prevents later listeners from running.