watch method

Stream<Query<T>> watch({ bool triggerImmediately = false, })

Finish building a Query creating a stream that issues events whenever queried entity changes. Streamed query is persisted between stream events and closed when you cancel the subscription.

if you pass TRUE as the triggerImmediately argument, a single stream event will be sent immediately after subscription. You can use this to get access to the query object before any data changes.

Implementation

Stream<Query<T>> watch({bool triggerImmediately = false}) {
  final queriedEntities = HashSet<Type>();
  _fillQueriedEntities(queriedEntities);
  final query = build();
  late StreamSubscription<void> subscription;
  late StreamController<Query<T>> controller;
  final subscribe = () {
    subscription = _store.entityChanges.listen((List<Type> entityTypes) {
      if (entityTypes.any(queriedEntities.contains)) {
        controller.add(query);
      }
    });
  };
  controller = StreamController<Query<T>>(
      onListen: subscribe,
      onResume: subscribe,
      onPause: () => subscription.pause(),
      onCancel: () => subscription.cancel());
  if (triggerImmediately) controller.add(query);
  return controller.stream;
}