Generator Trait

The GeneratorTrait provides an implementation of the GeneratorInterface to accumulate events and release them at a later time. There are two methods provided by this trait:

• public function releaseGeneratedEvents
• protected function addEvent

The addEvent method’s visibility is protected to ensure events are only added from within, preventing outside interference and to ensure the implementor has full control over which events are emitted.

Implementation Example

use League\Event\GeneratorTrait;
use League\Event\GeneratorInterface;

class User implements GeneratorInterface
{
    use GeneratorTrait;

    public function updateAddress(Address $address)
    {
        $this->address = $address;
        $this->addEvent(new UserAddressWasChanged($this, $address));
    }
}

$user = new User;
$user->updateAddress(new Address(...));

Emitting and Releasing Generated Events

Once events are generated, you’ll want to release them so they can be emitted. The GeneratorInterface specifies a releaseGeneratedEvents which returns an array of events to be emitted.

$events = $user->releaseGeneratedEvents();
$emitter->emitBatch($events);

// Or the shorter version
$emitter->emitGeneratedEvents($user);

When you prefer a more expressive syntax you can alter the addEvent method name like so:

class User
{
    use GeneratorTrait {
        addEvent as recordThat;
    }

    public function updateAddress(Address $address)
    {
        $this->address = $address;
        $this->recordThat(new UserAddressWasChanged($this, $address));
    }
}