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Dead simple event broker

Minimalistic bidirectional event broker for Dart. #

Introduction #

This package helps building event-driven systems by providing a small set of components:

Transport, Broker, Manager, Event.

Designed for full modularity and easy integration they can be combined to create topologies of any shape and complexity.

Either via static or dynamic configuration at runtime.

Bidirectional communication between transport and managers is supported out of the box.

Example topology #

architecture

API at a glance #

class TopicEvent 
  String topic // identifier
  String cmd
  dynamic payload

abstract class TopicManager
  String get topic // event destination
  handleEvent(TopicEvent) // consume incoming event
  sendEvent(TopicEvent) // produce outgoing event


abstract class TopicEventTransport
  onReceive(TopicEvent) // forward to broker
  onSend(TopicEvent) // receive from broker


class TopicEventBroker
  addManager(TopicManager)
  setTransport(TopicEventTransport)

Usage #

Set up the transport:

class MySocket extends TopicEventTransport {
  void connect() =>
      // BYO event source (sync or async)
      // call *onReceive* to forward incoming events to the broker
      myEventStream.listen(onReceive);

  // must override to handle outgoing events
  @override
  void onSend(TopicEvent event) => myEventSink.add(event);
}

Define one or more managers:

class MyManager extends TopicManager {
  // override to set the topic identifier
  @override
  Topic get topic => 'my_topic';

  // override to handle incoming events
  @override
  void handleEvent(TopicEvent event) {
    // do something with the event
    // call *sendEvent* to trigger outgoing my_topic events
    sendEvent('add', 'some data');
  }
}

Pass the transport and managers to the broker:

final socket = MySocket();

TopicEventBroker()
  // add as many managers as you need
  // adding a manager for an existing topic will replace the existing manager
  ..addManager(MyManager())
  ..addManager(MyOtherManager())
  // a broker can only have one transport at a time
  // on the other hand, a transport can handle multiple brokers, broadcasting incoming events
  // calling *setTransport* repeatedly will replace the existing transport and deregister the broker from it  
  ..setTransport(socket);

socket.connect();
socket.myEvents.add(TopicEvent('my_topic', 'do', 'something')); // -> MyManager
socket.myEvents.add(TopicEvent('my_other_topic', 'show', '{"arbitrary": "data"}')); // -> MyOtherManager

License #

MIT