Events

DryerJS does not emit events by default. However, you can easily add them by using a General Hook combines with @nestjs/event-emitter. NestJS document can be found here (opens in a new tab).

Installation

First you need to install @nestjs/event-emitter:

npm i --save @nestjs/event-emitter

Implementation

Below example, we create a General Hook to emit events when a record of any model is created, updated or removed. Then there is a EmailService that listens to the user.created event and send a welcome email to the user.

import {
  EventEmitter2,
  EventEmitterModule,
  OnEvent,
} from '@nestjs/event-emitter';
 
type Context = {};
 
@Injectable()
export class EventEmitterHook {
  constructor(private readonly eventEmitter: EventEmitter2) {}
 
  @AfterCreateHook(() => AllDefinitions)
  async fireAfterCreateEvents(input: AfterCreateHookInput<any, Context>) {
    this.eventEmitter.emit(`${input.definition.name}.created`, input);
  }
 
  @AfterUpdateHook(() => AllDefinitions)
  async fireAfterUpdateEvents(input: AfterUpdateHookInput<any, Context>) {
    this.eventEmitter.emit(`${input.definition.name}.updated`, input);
  }
 
  @AfterRemoveHook(() => AllDefinitions)
  async fireAfterRemoveEvents(input: AfterRemoveHookInput<any, Context>) {
    this.eventEmitter.emit(`${input.definition.name}.removed`, input);
  }
}
 
@Injectable()
class EmailService {
  @OnEvent('User.created')
  async handleOrderCreatedEvent({
    input,
  }: AfterCreateHookInput<User, Context>) {
    console.log(`Send welcome email to ${input.email}`);
  }
}
 
@Module({
  imports: [
    // other imports
    EventEmitterModule.forRoot(),
    DryerModule.register({
      definitions: [User],
      providers: [EventEmitterHook],
    }),
  ],
  providers: [EmailService],
})
export class AppModule {}
Access Module InputJWT