php-ddd / domain-event Goto Github PK

From your code I see that after an event is raised, it must be handled by a particular event listener. And this event listener must be registered in domain event locator, or you wont be able to execute the event. By doing this, you have to manually register event listener at some point of your code, and this is cumbersome. As the application grows and multiple events need to be triggered, it becomes complex to add event listeners manually.

I was wondering, why do you need this behavior? Why cannot you just implement the handler method inside the event object itself, so users do not have to register event listeners manually? Or maybe, you can make it possible to enable easy mapping between each event and its handler(if you want event to be ignorant of how it will be handlered), so the event locator will automatically create an event listener object for each event(ie. map event PurchaseOrderCreated to event listener PurchaseOrderCreatedHandler).

This way, when you iterate through events and publish them through event bus, the event bus will use event locator to automatically map an event to its listener. You wont need to register event listener/handler manually anymore, the code becomes more concise.

Of course, registration of custom event listeners/handlers introduce more flexibility, so it can always be left of as an option. I just personally think that registering event listeners manually can be problematic as the application grows, and it's also confusing where should we register event listeners(in MVC controller, application service, repository?).

You can test cody style in StyleCI and you can use Symfony preset.

https://github.com/php-ddd/domain-event/blob/master/src/AbstractAggregateRoot.php#L95

Event listeners should be able to listen to Event in as many way as the language allow us:

• direct class
• Interface
• parent class