api-add-event-handler

name	api-add-event-handler
description	Creates a domain event handler that reacts to events from another module (or the same module). Includes handler class and unit test. Use after domain events have been created with /api-add-domain-entity.

api-add-event-handler

Creates a domain event handler in the application layer. Event handlers react to domain events published by repositories after DB writes.

Project context

Read the ## Configuration section in .claude/CLAUDE.md for {SHARED_ROOT} and {MODULE_ROOT}.

Prerequisites

Run these skills first (in order):

1. /api-init-project — project scaffold
2. /api-setup-shared — shared base classes (DomainEvent, IDateProvider, etc.)
3. /api-add-module — module scaffold (application module with CqrsModule)
4. /api-add-domain-entity (with AggregateRoot) — creates the domain events this handler reacts to

Steps

1. Create handler — application/event-handlers/{action}-when-{event}.event-handler.ts Load references/event-handler-template.md.

   • Class name: {Action}When{Event}Handler (e.g., CreateWalletWhenUserCreatedHandler)
   • Decorate with @EventsHandler(XxxEvent)
   • Implement IEventHandler<XxxEvent> with handle(event) method
   • Inject dependencies via @Inject(TOKEN) — same pattern as command handlers

2. Create unit test — application/event-handlers/{action}-when-{event}.event-handler.spec.ts Load references/test-template.md.

   • Test using in-memory repositories
   • Construct the event directly and pass to handler.handle(event)
   • Assert on side effects (created entities, state changes)

3. Register handler — add the handler class to application/{module-name}.module.ts providers array. List the handler directly — no barrel file.

Limitations

• Does not create the domain event itself — events are created by /api-add-domain-entity.
• Event handlers are application-layer only — no HTTP/presentation logic.
• Cross-module event handlers: the handler module does NOT need to import the source module — only import the event class directly from the source module's domain layer.