Flutter Bloc Mediator

flutter_bloc_mediator is a Flutter package that facilitates message delegation between BLoCs using the Mediator pattern. This allows BLoCs to communicate without direct references, improving modularity and maintainability.

🚀 Why Use This Package?

🛑 Common Problems with BLoC Communication:

1. Direct Dependencies: BLoCs referencing each other lead to tight coupling and reduced testability.
2. Event Buses/Streams: Can be complex and hard to manage in large applications.
3. Global State Management: Often introduces unnecessary complexity.

✅ Solution: The Mediator Pattern

Instead of BLoCs directly referencing each other, they register themselves with a BlocHub and communicate using message passing.

📦 Installation

Add the package to your pubspec.yaml:

dependencies:
  flutter_bloc_mediator: latest_version

Then, install the package:

flutter pub get

🛠 Usage

1️⃣ Define a BLoC using BlocMember

import 'package:flutter_bloc_mediator/flutter_bloc_mediator.dart';

class CounterBloc with BlocMember {
  int counter = 0;

  @override
  void receive(String from, CommunicationType data) {
    if (data is CounterComType) {
      counter += data.value;
      
      // You can add new Event
      add(IncrementBlocBEvent(count: counter));
      
      print('$name received increment event from $from: Counter = $counter');
    }
  }
}

class CounterComType extends CommunicationType {
  final int value;
  CounterComType(this.value);
}

2️⃣ Create a BlocHub with BlocHubProvider

void main() {
  final blocHub = ConcreteHub();

  runApp(
    BlocHubProvider(
      blocHub: blocHub,
      child: MyApp(),
    ),
  );
}

3️⃣ Register BLoCs in the BlocHub with unique names

final counterBlocA = CounterBloc();
final counterBlocB = CounterBloc();

blocHub.registerByName(counterBlocA, 'CounterA');
blocHub.registerByName(counterBlocB, 'CounterB');

4️⃣ Local Bloc Usage

final CounterABloc aBloc = CounterABloc();
final CounterBBloc bBloc = CounterBBloc();

void setBlocMembers(BuildContext context) {
  BlocHubProvider.of(context).registerByName(aBloc, "CounterABloc");
  BlocHubProvider.of(context).registerByName(bBloc, "CounterBBloc");
}

@override
void initState() {
  WidgetsBinding.instance.addPostFrameCallback((_) {
    setBlocMembers(context);
  });
  super.initState();
}

@override
void dispose() {
  BlocHubProvider.of(context).removeByName("CounterABloc");
  BlocHubProvider.of(context).removeByName("CounterBBloc");
  super.dispose();
}

5️⃣ Global Bloc Usage with MultiBlocProvider

final CounterABloc aBloc = CounterABloc();
final CounterBBloc bBloc = CounterBBloc();

void setBlocMembers(BuildContext context) {
  BlocHubProvider.of(context).registerByName(aBloc, "CounterABloc");
  BlocHubProvider.of(context).registerByName(bBloc, "CounterBBloc");
}

@override
void initState() {
  WidgetsBinding.instance.addPostFrameCallback((_) {
    setBlocMembers(context);
  });
  super.initState();
}

MultiBlocProvider(
  providers: [
    BlocProvider<CounterABloc>(create: (context) => aBloc,),
    BlocProvider<CounterBBloc>(create: (context) => bBloc,)
  ],
  child: MaterialApp(
    title: 'Flutter Bloc Mediator Demo',
    theme: ThemeData(
      colorScheme: ColorScheme.fromSeed(seedColor: Colors.deepPurple),
      useMaterial3: true,
    ),
    home: const MyHomePage(),
  ),
);

5️⃣ Send messages between BLoCs

// Inside CounterA bloc
void _incrementCounter(CounterComType event, Emitter<CounterState> emit) {
  sendTo(CounterComType(2), 'CounterB');
}
// OR
counterBlocA.sendTo(CounterComType(2), 'CounterB');
counterBlocB.sendToAll(CounterComType(2));

6️⃣ Managing BlocHub Instances

Access the BlocHub instance:

BlocHubProvider.of(context)

Register a new BLoC:

BlocHubProvider.of(context).registerByName(aBloc, "CounterABloc");

Remove a registered BLoC:

BlocHubProvider.of(context).removeByName("CounterABloc");

Clear all registered BLoCs:

BlocHubProvider.of(context).clear();

📌 Example Output

CounterB received increment event from CounterA: Counter = 1
CounterA received increment event from CounterB: Counter = 2

🎯 Key Benefits

✅ Loose Coupling: BLoCs don’t need direct references to each other.
✅ Better Maintainability: Centralized communication logic in BlocHub.
✅ Improved Testability: Easily test individual BLoCs in isolation.

🤝 Contributing

Contributions are welcome! If you have ideas for improvements or find issues, feel free to open an issue or submit a pull request.

📜 License

This package is released under the MIT License.