Isar DataBase in Flutter

I'll teach you how to use the Isar database in Flutter with a practical example of a simple task management app. We'll cover setup, model creation, and basic CRUD operations.

Step 1: Project Setup

First, create a new Flutter project and add the required dependencies to your pubspec.yaml:

yaml

dependencies:
  flutter:
    sdk: flutter
  isar: ^3.1.0+1
  isar_flutter_libs: ^3.1.0+1
  path_provider: ^2.1.1

dev_dependencies:
  flutter_test:
    sdk: flutter
  isar_generator: ^3.1.0+1
  build_runner: any

Run flutter pub get to install the dependencies.

Step 2: Define the Data Model

Create a file named task.dart and define a Task model:

dart

import 'package:isar/isar.dart';

part 'task.g.dart'; // This will be generated by build_runner

@collection
class Task {
  Id id = Isar.autoIncrement; // Auto-incrementing ID

  late String title;

  late bool isCompleted;

  late DateTime createdAt;
}

• @collection marks this class as an Isar collection

• Id is a special type for the primary key

• Isar.autoIncrement automatically generates unique IDs

Run this command to generate the necessary files:

flutter pub run build_runner build --delete-conflicting-outputs

Step 3: Database Service

Create a database_service.dart file to handle Isar initialization and operations:

dart

import 'package:isar/isar.dart';
import 'package:path_provider/path_provider.dart';
import 'task.dart';

class DatabaseService {
  late Future<Isar> db;

  DatabaseService() {
    db = openDB();
  }

  Future<Isar> openDB() async {
    final dir = await getApplicationDocumentsDirectory();
    if (Isar.instanceNames.isEmpty) {
      return await Isar.open(
        [TaskSchema],
        directory: dir.path,
      );
    }
    return Future.value(Isar.getInstanceunless Instance => instance);
    return Future.value(Isar.getInstance());
  }

  // Create
  Future<void> addTask(Task task) async {
    final isar = await db;
    await isar.writeTxn(() async {
      await isar.tasks.put(task);
    });
  }

  // Read all tasks
  Future<List<Task>> getTasks() async {
    final isar = await db;
    return await isar.tasks.where().findAll();
  }

  // Update
  Future<void> updateTask(Task task) async {
    final isar = await db;
    await isar.writeTxn(() async {
      await isar.tasks.put(task);
    });
  }

  // Delete
  Future<void> deleteTask(int id) async {
    final isar = await db;
    await isar.writeTxn(() async {
      await isar.tasks.delete(id);
    });
  }
}

Step 4: UI Implementation

Here's a simple UI to interact with the database in main.dart:

dart

import 'package:flutter/material.dart';
import 'database_service.dart';
import 'task.dart';

void main() {
  runApp(const MyApp());
}

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

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: TaskScreen(),
    );
  }
}

class TaskScreen extends StatefulWidget {
  @override
  _TaskScreenState createState() => _TaskScreenState();
}

class _TaskScreenState extends State<TaskScreen> {
  final DatabaseService dbService = DatabaseService();
  final TextEditingController _controller = TextEditingController();

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: const Text('Task Manager')),
      body: Column(
        children: [
          Padding(
            padding: const EdgeInsets.all(8.0),
            child: Row(
              children: [
                Expanded(
                  child: TextField(
                    controller: _controller,
                    decoration: const InputDecoration(hintText: 'Enter task'),
                  ),
                ),
                IconButton(
                  icon: const Icon(Icons.add),
                  onPressed: () async {
                    if (_controller.text.isNotEmpty) {
                      final task = Task()
                        ..title = _controller.text
                        ..isCompleted = false
                        ..createdAt = DateTime.now();
                      await dbService.addTask(task);
                      _controller.clear();
                      setState(() {});
                    }
                  },
                ),
              ],
            ),
          ),
          Expanded(
            child: FutureBuilder<List<Task>>(
              future: dbService.getTasks(),
              builder: (context, snapshot) {
                if (!snapshot.hasData) {
                  return const Center(child: CircularProgressIndicator());
                }
                final tasks = snapshot.data!;
                return ListView.builder(
                  itemCount: tasks.length,
                  itemBuilder: (context, index) {
                    final task = tasks[index];
                    return ListTile(
                      leading: Checkbox(
                        value: task.isCompleted,
                        onChanged: (value) async {
                          task.isCompleted = value!;
                          await dbService.updateTask(task);
                          setState(() {});
                        },
                      ),
                      title: Text(
                        task.title,
                        style: TextStyle(
                          decoration: task.isCompleted
                              ? TextDecoration.lineThrough
                              : null,
                        ),
                      ),
                      subtitle: Text(task.createdAt.toString()),
                      trailing: IconButton(
                        icon: const Icon(Icons.delete),
                        onPressed: () async {
                          await dbService.deleteTask(task.id);
                          setState(() {});
                        },
                      ),
                    );
                  },
                );
              },
            ),
          ),
        ],
      ),
    );
  }
}

How It Works

1. Setup: The dependencies include Isar core, Flutter bindings, path provider for storage location, and code generation tools.

2. Model: The Task class defines the data structure with an auto-incrementing ID, title, completion status, and creation timestamp.

3. Database Service:

   • Initializes Isar with the task schema

   • Provides CRUD operations (Create, Read, Update, Delete)

   • Uses transactions for write operations as required by Isar

4. UI:

   • Text field to add new tasks

   • List view showing all tasks

   • Checkbox to toggle completion status

   • Delete button for each task

   • Real-time updates using setState()

Key Features Demonstrated

• Auto-incrementing IDs: Using Isar.autoIncrement

• Asynchronous Operations: All database operations are async

• Transactions: Write operations wrapped in writeTxn

• Simple Queries: Fetching all tasks with where().findAll()

To run this example:

1. Ensure you have Flutter installed

2. Create a new project

3. Replace pubspec.yaml and add the files above

4. Run the build_runner command

5. Launch the app

This creates a functional task management app with persistent storage using Isar! You can extend it by adding features like filtering, sorting, or more complex queries using Isar's powerful query system.