Class EventHandler

A Handler that allows subscribers (any caller) to subscribe to a specific event

All subscribers will be notified if the EventHandler dispatched the event.

Example

At first the EventHandler has to be created with a unique name that subscribes the purpose.

• the generic can be of any type / interface
• to create a handler which only handles "notification" (without payload) the generic has to be <void>
• the unique name gets relevant when combining EventHandlers with EventCombiners

const StringEventHandler = new EventHandler<string>('StringEventHandler');

To receive messages from the handler, a subscription has to be made with a unique name.

• the name of the subscription is relevant when handling multiple subscribers an referencing when unsubscribing
• the event which is provided in the callback is a DomainEvent with the dispatched payload (typed)

StringEventHandler.subscribe('StringEventLogger', (event) => {
  console.log(event.payload);
});

To send messages a dispatch with the correctly typed value has to be made.

StringEventHandler.dispatch('my payload'); // StringEventLogger logs 'my payload'

When a Subscription is unsubscribed, the callback will no longer be called

StringEventHandler.unsubscribe('StringEventLogger');
StringEventHandler.dispatch('another payload'); // StringEventLogger is no longer notified

Logging

To use the logging functionality the handler has to be extended to activate the following logging methods:

• protected logSubscribe(name: string) - log when .subscribe() is called
• protected logUnsubscribe(name: string) - log when .unsubscribe() is called
• protected logDispatch() - log when dispatch() is called
• protected logDispatchedSubscription(subscription: Subscription<Payload>) - log when a subscription is notified