flutter_sync_engine 1.0.3

A Flutter offline-first sync engine plugin for local operation logging, push/pull transport, and conflict resolution.

Flutter SyncEngine

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SyncEngine is a lightweight Flutter/Dart package that helps developers sync data between local storage and remote backends.
It is flexible and backend-agnostic, allowing you to use any storage (File, Hive, SQLite, etc.) and any transport (REST API, dummy transport, or custom).

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Features

• Push and pull data to/from a backend.
• Local storage support (File, Hive, SQLite, or custom).
• Full CRUD support including deletion (deleteEntity now supported in all example stores).
• Conflict resolution support (LastWriteWins by default, custom resolvers allowed).
• Backend-agnostic: transport can be REST, GraphQL, WebSocket, or custom.
• Minimal dependencies – you can choose your storage/transport freely.
• MockSyncStore for testing and unit tests.

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Installation

Add to your pubspec.yaml:

dependencies:
  flutter_sync_engine: <latest_version>

Usage

Import package

import 'package:flutter_sync_engine/flutter_sync_engine.dart';

Initialise store and transport

  final store = await FileSyncStore.create('notes.json'); // File store
  final transport = DummyTransport(); // Dummy transport

  final engine = SyncEngine(store: store, transport: transport);
  engine.registerCollection(name: 'notes', conflictResolver: const LastWriteWins());

Add, Delete & Sync Data

// Add note locally
final note = {
    'id': '1',
    'title': 'Note 1',
    'content': 'This is a note',
    'updatedAt': DateTime.now().toIso8601String(),
};
await store.saveEntity('notes', note);
await store.logOperation(SyncOperation(
collection: 'notes',
entityId: note['id']!,
type: OperationType.create,
timestamp: DateTime.now(),
data: note,
));

// Delete note
await store.deleteEntity('notes', note['id']!);
await store.logOperation(SyncOperation(
collection: 'notes',
entityId: note['id']!,
type: OperationType.delete,
timestamp: DateTime.now(),
data: {},
));

// Sync with backend
await engine.sync();

RestTransport Example [sync with REST API]

final transport = RestTransport('YOU_API_HERE');//Dummy API
await engine.sync(); // Push local notes and pull remote notes

Conflict Resolution

• By Default LastWriteWins is used:

  class LastWriteWins implements ConflictResolver { @override Map<String, dynamic> resolve({ required Map<String, dynamic> local, required Map<String, dynamic> remote, }) { final localUpdated = DateTime.parse(local['updatedAt'] ?? '1970-01-01'); final remoteUpdated = DateTime.parse(remote['updatedAt'] ?? '1970-01-01'); return localUpdated.isAfter(remoteUpdated) ? local : remote; } }

• You can also implement a custom resolver per collection:

    engine.registerCollection(
    name: 'notes',
    conflictResolver: MyCustomResolver(),
    );
  

Store Options

Store Type	Description
FileSyncStore	Simple JSON file storage (supports create, update, delete)
HiveSyncStore	Persistent NoSQL storage using Hive (supports create, update, delete)
SQLiteSyncStore	Relational storage using SQLite (supports create, update, delete)
MockSyncStore	In-memory store for testing and unit tests
Custom	You can implement SyncStore interface for your own storage (full CRUD)

Transport Options

Transport Type	Description
DummyTransport	In-memory backend for testing
RestTransport	Connects to a REST API
Custom	Implement SyncTransport for your own backend