OSAM #

Osam is a Lightweight library to manage and notify the state.

The core element is PropertyNotifier.

PropertyNotifier allows you to change a value and notify everything listening to it.

Same as ValueNotifier you can add listeners and remove listeners.

To decide should listeners get a notification, PropertyNotifier uses Equatable and storing last known "good" hashcode. It allows you to use mutable data in the domain layer safe.

PropertyNotifier implements IProperty to prevent the setting of new value from the presentation layer.

IProperty very actively uses in osam_flutter and good fits with it.

Example:

import 'package:flutter/material.dart';
import 'package:osam/osam.dart';

class Counter {
  // good constructor structure for restoring entity from hive
  Counter([this._value]) {
    _value ??= PropertyNotifier(0);
  }

  PropertyNotifier<int> _value;

  IProperty<int> get value => _value;

  void increment() => _value.value++;
}

void main() {
  final counter = Counter();
  runApp(Example(counter: counter));
}

class Example extends StatelessWidget {
  final Counter counter;

  const Example({Key key, this.counter}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        floatingActionButton: FloatingActionButton(
          child: Icon(Icons.add),
          onPressed: () => counter.increment(),
        ),
        body: Center(
          child: ValueListenableBuilder(
            valueListenable: counter.value,
            builder: (_, value, __) => Text(
              value.toString(),
              style: const TextStyle(fontSize: 40),
            ),
          ),
        ),
      ),
    );
  }
}

Also, you can use the Persist repository to store your AppState and UIState. osam_flutter uses a persist repository to store all-state.

If you prefer to follow clean architecture principles, I recommend you to write use-case to change the state of the application. Usecase could be easily provided by UseCaseContainer