Skip to main content

EventBus

The EventBus publishes and subscribes to domain events.

Class Definition​

class EventBus implements EventBusInterface {
  constructor();
  
  publish<TEvent extends UntypedDomainEventType>(
    event: TEvent
  ): Promise<PublishResultInterface>;
  
  on<TEvent extends UntypedDomainEventType>(
    eventType: TEvent["type"],
    handler: LocalEventHandler<TEvent>
  ): () => void;
}

Constructor​

new EventBus()​

Creates a new EventBus instance.

Example:

const eventBus = new EventBus();

Methods​

on<TEvent>(eventType, handler): () => void​

Subscribes to events of a specific type.

Type Parameters:

  • TEvent - The event type (must extend UntypedDomainEventType)

Parameters:

  • eventType: TEvent["type"] - The event type string
  • handler: LocalEventHandler<TEvent> - The event handler 
    type LocalEventHandler<T extends UntypedDomainEventType> = (
      event: DomainEventInterface<T["type"], T["payload"]>
    ) => void | Promise<void>;

Returns: Unsubscribe function

Example:

const unsubscribe = eventBus.on("TodoCreated", async (event) => {
  console.log("Todo created:", event.payload);
});

publish<TEvent>(event): Promise<PublishResultInterface>​

Publishes an event to all registered handlers.

Type Parameters:

  • TEvent - The event type

Parameters:

  • event: TEvent - The event to publish

Returns: Promise<PublishResultInterface> - Results from all handlers

Example:

const event = new TodoCreatedEvent({ id: "123", text: "Learn xndr" });
const results = await eventBus.publish(event);

Interface​

interface EventBusInterface {
  publish<TEvent extends UntypedDomainEventType>(
    event: TEvent
  ): Promise<PublishResultInterface>;
  
  on<TEvent extends UntypedDomainEventType>(
    eventType: TEvent["type"],
    handler: LocalEventHandler<TEvent>
  ): () => void;
}