pubsub

kz is a collection of easy-to-use utility and feature libraries for creating anything you want with the Deno runtime.

@kz/pubsub

The @kz/pubsub module provides types and features for implementing the publisher/subscriber pattern.

Overview | API Docs

Within integereleven the publisher/subscriber pattern is a software design pattern similar to the observer pattern, but with a key difference: topics. In the publisher/subscriber pattern, the publisher sends messages to subscribers based on topics. This allows for more granular control over which messages are sent to which subscribers.

Examples

import {
  type PubSubTopicMessage,
  TAbstractSubscriber,
  TBasePublisher,
} from './mod.ts';

import { TAbstractObserver } from '@kz/observe';

interface TChange<T> {
  model: string;
  user: string;
  value: T;
}

interface IUser {
  id: string;
  name: string;
}

interface IDevice {
  id: string;
  name: string;
  type: string;
}

type ChangeMap = {
  'user': TChange<IUser>;
  'device': TChange<IDevice>;
};

class Updater extends TBasePublisher<ChangeMap> {
}

class UserUpdater extends TAbstractSubscriber<ChangeMap, 'user'> {
  public next(change: PubSubTopicMessage<ChangeMap, 'user'>): void {
    const [, message] = change;

    console.log(
      `User ${message.user} updated ${message.model} to ${message.value.name}`,
    );
  }

  public error(error: Error): void {
    console.error(error);
  }
}

class DeviceUpdater extends TAbstractSubscriber<ChangeMap, 'device'> {
  public next(change: PubSubTopicMessage<ChangeMap, 'device'>): void {
    const [, message] = change;

    console.log(
      `User ${message.user} updated ${message.model} to ${message.value.name}`,
    );
  }

  public error(error: Error): void {
    console.error(error);
  }
}

// Yes! You can use regular observers to subscribe to a publisher.
// Because they cannot specify a topic, they will receive all messages from
// the publisher.
class Logger extends TAbstractObserver<PubSubTopicMessage<ChangeMap>> {
  public next(change: PubSubTopicMessage<ChangeMap>): void {
    const [topic, message] = change;

    console.log(`${topic}: Changed by ${message.user}`);
  }

  public error(error: Error): void {
    console.error(error);
  }
}

const updater = new Updater();
const userUpdater = new UserUpdater(['user']);
const deviceUpdater = new DeviceUpdater(['device']);
const logger = new Logger();

updater.subscribe(userUpdater);
updater.subscribe(deviceUpdater);
updater.subscribe(logger);

updater.publish(['user', {
  model: 'user',
  user: 'admin',
  value: { id: '1', name: 'admin' },
}]);

updater.publish(['device', {
  model: 'device',
  user: 'admin',
  value: { id: '1', name: 'MKSENSE', type: 'sensor' },
}]);

Contributing

Contributions are welcome! Take a look at our contributing guidelines to get started.

License

The MIT License (MIT) 2020-2024 integereleven. Refer to LICENSE for details.

_{Built with ❤ by integereleven}