An example of a basic StreamController and StreamSubscription

streams101.dart

import 'dart:async';


class Person {
  final String firstName;
  final String lastName;
  Person({required this.firstName, required this.lastName});

  factory Person.fromMap(Map<String, dynamic> m) {
    return Person(
        firstName: m['firstName'] ?? "", lastName: m['lastName'] ?? "");
  }

  @override
  String toString() {
    return "Person(firstName=$firstName, lastName=$lastName)";
  }
}

void main() async {
  final StreamController<Map<String, dynamic>> ctrl = StreamController();
  final StreamSubscription subscription = ctrl.stream.listen((data) => data,
      onError: (e) => print("Error: $e"), onDone: () => print('Yay!!!'));
  ctrl.sink.add({'firstName': "Joe", 'lastName': "Shmoe"});
  ctrl.sink.add({'firstName': "Vivian", "lastName": "Fox"});
  ctrl.sink.add({'firstName': "Gary", "lastName": "Larson"});
  ctrl.sink.add({"firstName": "Elijah"});
  ctrl.sink.addError('Yer mum!');
  ctrl.sink.add({"name": "Drew Barrymore"});

  subscription.onData((data) {
    if (validateMap(data)) print(Person.fromMap(data));
  });
  subscription.onDone(() => print("All done!"));
  await ctrl.close();
}



bool validateMap(Map m) {
  return m.keys.contains('firstName') && m.keys.contains('lastName');
}