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Classes ​

Every consumer and topic can be written as a class instead of with the builder. Both produce the same definition, so dispatch, AsyncAPI and the client see no difference. Reach for a class when consumers share logic through a base class, or when a hook reads better as a method to override.

Consumers ​

One instance serves one connection, so its fields are per-connection state:

ts
import {
  AsyncJsonWebsocketConsumer,
  Consumer,
  On,
} from '@chanx-js/server';

@Consumer('/ws/chat/{room}', { name: 'chat', emits: [Notice] })
class ChatConsumer extends AsyncJsonWebsocketConsumer<User> {
  messages = 0;

  @On(PingMessage, { output: PongMessage })
  ping() {
    return PongMessage.create();
  }

  @On(Chat)
  async chat(m: MessageOf<typeof Chat>) {
    this.messages++;
    await this.push(
      Notice.create({
        text: `${this.params.room}: ${m.payload.text}`,
      }),
    );
  }

  override onConnect() {
    console.log(`${this.conn.user.name} joined`);
  }
}

createChanx({ consumers: [ChatConsumer] });

The decorators work with standard decorators and with experimentalDecorators. A subclass method overrides the handler of the same name, decorated or not, and two methods handling one action are an error. @OnEvent handles events; the error hooks are methods to override.

Topics ​

One instance serves one subscription. The class name names the layer group, so two servers sharing a layer must use the same name:

ts
import { On, Topic } from '@chanx-js/server';

class RoomTopic extends Topic {
  static override pattern = 'room:{room_name}';
  static override passthrough = [RoomEvent];

  override authorize() {
    return this.params.room_name !== 'secret';
  }

  @On(Post, { output: Posted })
  async post(m: MessageOf<typeof Post>) {
    await this.publish(RoomEvent.create(m.payload));
    return Posted.create(m.payload);
  }
}

consumer('/ws/hub', { name: 'hub', topics: [RoomTopic] });

topicConsumer(RoomTopic, '/ws/room/{room_name}') serves a class topic on its own route.

On NestJS ​

@chanx-js/nestjs takes the same approach with its own decorators, @ChanxConsumer and @ChanxTopic, on injectable classes: a gateway gets Nest's DI, guards and pipes as well.

MIT licensed