Bloc Provider

bloc_provider Codemagic build status

Provides BLoC(Business Logic Component) to descendant widget (O(1)), and the bloc is disposed automatically by the state which the bloc_provider holds internally.


1. Define some BLoC like this:

class CounterBloc implements Bloc {
  final _countController = BehaviorSubject<int>.seeded(0);
  final _incrementController = PublishSubject<void>();

  CounterBloc() {
        .scan<int>((sum, _v, _i) => sum + 1, 0)

  ValueStream<int> get count => _countController;
  Sink<void> get increment => _incrementController.sink;

  void dispose() async {
    await _incrementController.close();
    await _countController.close();

2. Provide the bloc by using BlocProvider and access the bloc at subtree:

void main() => runApp(
      // Create and provide the bloc.
        creator: (_context, _bag) => CounterBloc(),
        child: App(),

class App extends StatelessWidget {
  Widget build(BuildContext context) {
    // Access the bloc with O(1) computation complexity.
    final bloc = BlocProvider.of<CounterBloc>(context);
    return MaterialApp(
      home: Scaffold(
        body: Center(
          child: StreamBuilder<int>(
            stream: bloc.count,
            initialData: bloc.count.value,
            builder: (context, snap) => Text(
                  'count: ${}',
                  style: Theme.of(context).textTheme.title,
        floatingActionButton: FloatingActionButton(
          child: const Icon(Icons.add),
          onPressed: () => bloc.increment.add(null),
  • Computational complexity of of method, which is used for accessing the bloc is O(1).
  • Provided bloc will be disposed when the inner state is disposed 👍


Technical explanation

Features and bugs

Please file feature requests and bugs at the issue tracker.

• Released: Apr 23, 2020, 06:07 AM

Bloc Provider

Author: mono0926
Item was Featured Author was Featured Bought between 100 and 500 items Referred more than 1000 members Author had a Free File of the Month Contributed a Blog Post Helped protect FrontendFun against copyright violations Reviewer FrontendFun Developer Site Administrator Moderator Blog Editor
Provides bloc to descendant widget (O(1)), and the bloc is disposed appropriately by state that the bloc_provider holds internally. size
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