spread 0.0.8

Easiest to implement state management for Flutter. Use any primitive, enum, type or entity as state. Support state event multicasting

example/lib/main.dart

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

import '../fullDemo/pages/home/widgets/posts.dart';
import '../fullDemo/pages/home/widgets/users.dart';
import '../fullDemo/services.dart';
import '../fullDemo/users/user_states.dart';

void main() {
  UsersObserver().selfRegister();
  runApp(const MyApp());
}

// The DemoApp has two states defined by the AppState enum.

enum AppState { users, posts }

class MyApp extends StatelessWidget {
  const MyApp({super.key});

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Spread Demo App',
      debugShowCheckedModeBanner: false,
      theme: ThemeData(
        colorScheme: ColorScheme.fromSeed(seedColor: Colors.blue),
        useMaterial3: true,
      ),
      home: HomePage(),
    );
  }
}

// A demo page with BottomNavigationBar.
// - the body is built depending of the state of type AppState

class HomePage extends StatelessWidget with StateEmitter {
  HomePage({super.key});

  @override
  Widget build(BuildContext context) {
    // set initial states
    emit<AppState>(AppState.users);
    LoadUsersUseCase().execute();

    return Scaffold(
        appBar: _appbar,
        bottomNavigationBar: _navigator(context),
        body: Spread<AppState>(
          builder: _homeBody,
        ));
  }

  Widget _homeBody(BuildContext context, AppState? state) {
    switch (state) {
      case AppState.posts:
        {
          return PostsPage();
        }
      case AppState.users:
      default:
        {
          return UsersPage();
        }
    }
  }

  AppBar get _appbar => AppBar(
        title: const Text('Spread Full Demo'),
      );

  BottomNavigationBar _navigator(BuildContext context) => BottomNavigationBar(
        onTap: onNavigatorTap,
        items: const <BottomNavigationBarItem>[
          BottomNavigationBarItem(
            icon: Icon(Icons.account_circle),
            label: 'Users',
          ),
          BottomNavigationBarItem(
            icon: Icon(Icons.data_array),
            label: 'Posts',
          ),
        ],
      );

  Future onNavigatorTap(int index) async {
    print('navigator tap: $index');
    switch (index) {
      case 0:
        {
          showUsers();
          break;
        }
      case 1:
        {
          showPosts();
          break;
        }
    }
  }

  void showUsers() async {
    LoadUsersUseCase().execute();
    emit<AppState>(AppState.users);
  }

  void showPosts() async {
    emit<AppState>(AppState.posts);
  }
}

// Create a UseCase to perform actions and notify states

class LoadUsersUseCase with StateEmitter implements UseCase {
  @override
  void execute() async {
    emit<UsersState>(LoadingUsers());
    Services().userService.getUsers().then((users) {
      emit<UsersState>(LoadedUsersSuccess(users: users));
    }).onError((error, stackTrace) {
      emit<UsersState>(LoadedUsersFail(error: error, stackTrace: stackTrace));
    });
  }
}

// Create a State observer service to listen and handle states asynchronously

class UsersObserver extends SpreadObserver<UsersState> {
  @override
  onState(UsersState state) {
    print("UsersObserver Observed: ${state.toString()}");
  }
}