State Provider

A super simple state management library for Flutter.

The whole implementation is less than 200 lines of code, including docs comments. It uses no external libraries and is therefore really easy to integrate and debug.

Super simple doesn't mean poorly implemented, though. It's actually pretty powerful:

• 🪨 Built around immutable values, making it easier to keep track of state changes.
• 🌌 Full support for streams, allows states to interact with each other.
• 🕹️ Efficient separation of states data from states mutation logic.
• ✨ Convenient access to states directly from the context.
• 🧹 Automatic dispose of states when they are no longer used.

Inspired by popular libraries like Provider and Bloc, but built around Flutter's existing tools like Listenable, StreamController, and InheritedNotifier.

And it's fully covered by tests 💯.

Getting Started

Installation

Add this to your pubspec.yaml file:

dependencies:
  state_provider:
    git:
      url: https://github.com/Riki1312/state-provider.git

Then run flutter pub get.

Counter example

Create a class that contains the counter state and extends StateValue.

class CounterState extends StateValue<int> {
  CounterState() : super(0);

  void increment() {
    value++;
  }
}

Use the StateProvider widget to inject the state into the tree.

StateProvider(
  state: CounterState(),
  child: ...,
);

Retrieve the state from a descendant widget of the StateProvider.

(This uses the type of the state, in this case CounterState).

Builder(
  builder: (context) => Text('${context.watch<CounterState>().value}'),
),

ElevatedButton(
  onPressed: () {
    context.read<CounterState>().increment();
  },
  child: ...,
),

The difference between context.watch and context.read is that watch rebuilds the widget whenever the state value changes, while read only returns the state.

Counter example with streams

Thanks to the streams we can extend the previous example by adding a second state that works with the first to keep track of odd numbers inside a list.

class ListState extends StateValue<List<String>> {
  ListState(CounterState counterState) : super([]) {
    sub = counterState.stream.where((number) => number.isOdd).listen((number) {
      value = [...value, "Odd: $number"];
    });
  }

  StreamSubscription? sub;

  @override
  Future<void> onClose() async => sub?.cancel();
}

Let's add another StateProvider for the new state.

StateProvider(
  state: ListState(context.read<CounterState>()),
  child: ...,
),

Now we can use the new state in the widget tree.

Builder(
  builder: (context) => Text('${context.watch<ListState>().value}'),
),

Counter example alternative

Instead of creating a new class for very simple cases, you can use StateValue directly.

StateProvider(
  state: StateValue<int>(0),
  child: ...,
),

Builder(
  builder: (context) => Text('${context.watch<StateValue<int>>().value}'),
),

ElevatedButton(
  onPressed: () {
    context.read<StateValue<int>>().value++;
  },
  child: ...,
),

Contributing and Feedback

If you have any questions or suggestions, feel free to open an issue or a pull request.

License

Licensed under the MIT License.