Local First #

Local-first data layer for Flutter apps that keeps your data available offline and synchronizes when the network returns. The goal is to provide a lightweight, pluggable engine that works with common local stores (Hive, SQLite, etc.) and can sync to any backend through custom strategies.

Status: early preview. The package is in active development (final stages) and the public API may change before the first stable release. Use the examples below as guidance for the intended design.

Why local_first? #

• Fast, responsive apps that read/write locally first and sync in the background.
• Works without a network connection; queues changes and resolves conflicts when back online.
• Storage-agnostic: start with our Hive, SQLite, or your preferred custom database implementation.
• Backend-agnostic: create your sync strategies, so you can integrate with your existent REST, gRPC, WebSockets, etc.
• Minimal boilerplate: declare the storage, register your models with repositories, and start syncing.

Features #

• Offline-first caching with automatic retry when connectivity is restored.
• Typed repositories for common CRUD flows.
• Conflict handling strategies (last-write-wins, timestamps, and custom resolution hooks).
• Background sync hooks for push/pull cycles.
• Encryption-ready storage layer by leveraging your chosen database/provider.
• Dev-friendly: simple configuration, verbose logging, and test utilities.

Installation #

Add the dependency to your pubspec.yaml:

dependencies:
  local_first: ^0.5.0
  local_first_hive_storage: ^0.0.1  # optional
  local_first_sqlite_storage: ^0.0.1 # optional

Then install it with:

flutter pub get

Quick start #

The API is evolving, but the intended flow looks like this:

import 'package:local_first/local_first.dart';

// 1) Describe your model and add LocalFirstModel to get sync metadata.
class Todo with LocalFirstModel {
  Todo({
    required this.id,
    required this.title,
    this.completed = false,
  }) : updatedAt = DateTime.now();

  final String id;
  final String title;
  final bool completed;
  final DateTime updatedAt;

  @override
  Map<String, dynamic> toJson() => {
        'id': id,
        'title': title,
        'completed': completed,
        'updated_at': updatedAt.toIso8601String(),
      };

  factory Todo.fromJson(Map<String, dynamic> json) => Todo(
        id: json['id'] as String,
        title: json['title'] as String,
        completed: json['completed'] as bool? ?? false,
        updatedAt: DateTime.parse(json['updated_at']),
      );

  // Last write wins.
  static Todo resolveConflict(Todo local, Todo remote) =>
      local.updatedAt.isAfter(remote.updatedAt) ? local : remote;
}

// 2) Create a repository for the model.
final todoRepository = LocalFirstRepository<Todo>.create(
  name: 'todo',
  getId: (todo) => todo.id,
  toJson: (todo) => todo.toJson(),
  fromJson: Todo.fromJson,
  onConflict: Todo.resolveConflict,
);

Future<void> main() async {
  // 3) Wire up local storage plus your sync strategy.
  final client = LocalFirstClient(
    repositories: [todoRepository],
    // Choose your adapter (add dependency and import it):
    // import 'package:local_first_hive_storage/local_first_hive_storage.dart';
    // import 'package:local_first_sqlite_storage/local_first_sqlite_storage.dart';
    localStorage: HiveLocalFirstStorage(), // or SqliteLocalFirstStorage()
    syncStrategies: [
      // Provide your own strategy that implements DataSyncStrategy.
      MyRestSyncStrategy(),
    ],
  );

  await client.initialize();

  // 4) Use the repository as if you were online the whole time.
  await todoRepository.upsert(Todo(id: '1', title: 'Buy milk'));

  // served instantly from local cache
  final todoStream = todoRepository.query().orderBy('title').watch();

  // 5) Let your strategy push/pull, or trigger manually when it makes sense.
  // await client.sync();
}

Choose your storage backend #

• Hive: schema-less, fast key/value boxes. Add local_first_hive_storage and use HiveLocalFirstStorage() (default in the basic example).
• SQLite: structured tables with indexes for query filters/sorts. Add local_first_sqlite_storage and use SqliteLocalFirstStorage(), providing a schema when creating repositories:

final todoRepository = LocalFirstRepository<Todo>.create(
  name: 'todo',
  getId: (todo) => todo.id,
  toJson: (todo) => todo.toJson(),
  fromJson: Todo.fromJson,
  onConflict: Todo.resolveConflict,
  schema: const {
    'title': LocalFieldType.text,
    'completed': LocalFieldType.boolean,
    'updated_at': LocalFieldType.datetime,
  },
);
final client = LocalFirstClient(
  repositories: [todoRepository],
  localStorage: SqliteLocalFirstStorage(),
  syncStrategies: [MyRestSyncStrategy()],
);

Example app #

A starter Flutter app lives in example/ and showcases the local-first flow to increment or decrement a global shared counter (per-user namespaces, repositories, and a Mongo sync mock).

# Clone and fetch deps
git clone https://github.com/rafaelsetragni/local_first.git
cd local_first
flutter pub get

# Run the sample
cd example
flutter pub get
flutter run

# (Optional) Start the Mongo mock used by the sync strategy.
# docker run -d --name mongo_local -p 27017:27017 \\
#   -e MONGO_INITDB_ROOT_USERNAME=admin \\
#   -e MONGO_INITDB_ROOT_PASSWORD=admin mongo:7

Roadmap #

• ✅ Implement Hive and SQLite storage adapters via add-on packages.
• ❌ Provide REST and WebSocket sync strategies via add-on packages.
• ❌ Background sync helpers for Android/iOS via add-on packages.
• ✅ End-to-end sample app with authentication.
• ✅ Comprehensive docs and testing utilities (models now use LocalFirstModel mixin; full test coverage added).

Contributing #

Contributions are welcome! Please open an issue to discuss ideas or bugs, and feel free to submit pull requests once we agree on the approach. Running the test suite before sending changes helps keep the package stable:

flutter test

License #

This project is available under the MIT License. See LICENSE for details.