Streamlining State Management in Flutter: The Evolution of BLoC

A New Era of State Management

Flutter, a relatively new cross-platform software development framework, has made significant strides in its short lifespan. One area where Flutter shines is state management, with BLoC (Business Logic Component) being one of the oldest and most reliable forms of state management within Flutter.

Breaking Changes and Migration

The latest release of flutter_bloc 8 brings some breaking changes that require users to upgrade their code manually. While this may seem daunting, the benefits of these changes far outweigh the effort required to migrate.

dependencies:
  flutter_bloc: ^8.0.0

The new implementation introduces event handlers, making it easier to work with streams and enabling apps to function in a more consistent and reliable manner.

The Limitations of mapEventToState

In the previous version of flutter_bloc, the mapEventToState function was central to state management. However, this function had several limitations:

• It was often long and cumbersome, making code readability suffer.
• It returned a Stream, which could lead to issues when working with streams.
• There was a timing problem with Dart that affected how streams worked.

Introducing Event Handlers

With the introduction of event handlers in flutter_bloc 8, the code is significantly shorter and more readable. Events are registered as event handlers, and responses are handled by calling emit with the new state.

on<MyEvent>((event, emit) {
  // Handle event and emit new state
  emit(MyState());
});

This change not only improves code readability but also eliminates the need to work with streams.

Migrating to flutter_bloc 8

To migrate to the new version of flutter_bloc, you’ll need to:

1. Upgrade your package in your pubspec.yaml file.
2. Set up event handlers and use events as the types of events that you register to listen to.

Long-Running Operations with await and Streams

In flutter_bloc 8, long-running operations with await are simplified, and the control flow is more logical.

on<MyEvent>((event, emit) async {
  // Perform long-running operation
  final result = await longRunningOperation();
  emit(MyState(result));
});

When working with streams, you can use await for to emit new states as the stream serves them up.

on<MyEvent>((event, emit) async {
  await for (final data in stream) {
    emit(MyState(data));
  }
});

This eliminates the need for yield generator functions, making the code more intuitive and easier to understand.