Hive Documentation

To store custom Dart objects, the object must implement .fromJson() and .toJson() methods. You must also register an adapter for the class using Hive.registerAdapter() before using it.

class Bee {
  Bee({required this.name, required this.role});

  factory Bee.fromJson(Map<String, dynamic> json) => Bee(
    name: json['name'] as String,
    role: json['role'] as String,
  );

  final String name;
  final String role;

  Map<String, dynamic> toJson() => {
    'name': name,
    'role': role,
  };
}

// Register the adapter
Hive.registerAdapter('Bee', Bee.fromJson);

// Use the box
final box = Hive.box();
final bumble = Bee(name: 'Bumble', role: 'Worker');
box.put('BumbleID', bumble);

Before using Hive, you must designate a directory where it can store its data. It is recommended to use path_provider to find the optimal directory for the current platform (e.g., getApplicationDocumentsDirectory()) and assign it to Hive.defaultDirectory.

void main() async {
  WidgetsFlutterBinding.ensureInitialized();
  final dir = await getApplicationDocumentsDirectory();
  Hive.defaultDirectory = dir.path;

  // ...
}

To use Hive in a Flutter project, create a new project and add the following dependencies to your pubspec.yaml file:

• hive: The core database engine.
• isar_flutter_libs: Required libraries for Hive/Isar functionality.
• path_provider: To access the device's local file system for storage.

dependencies:
  flutter: 
    sdk: flutter
  hive: ^4.0.0
  isar_flutter_libs: ^4.0.0-dev.13
  path_provider: ^2.0.0

Before using Hive in a Flutter application, you must ensure Flutter is initialized and set the Hive.defaultDirectory to a valid path on the device (typically the application documents directory) using path_provider.

import 'package:flutter/material.dart';
import 'package:hive/hive.dart';
import 'package:path_provider/path_provider.dart';

void main() async {
  WidgetsFlutterBinding.ensureInitialized();

  final directory = await getApplicationDocumentsDirectory();
  Hive.defaultDirectory = directory.path;

  runApp(BeeApp());
}

To use Hive in your Flutter or Dart project, add hive, isar_flutter_libs, and path_provider to your pubspec.yaml file. path_provider is used to locate the appropriate directory for data storage on different platforms.

dependencies:
  hive: ^4.0.0
  isar_flutter_libs: ^4.0.0-dev.13
  path_provider: ^2.1.0

Hive uses 'Boxes' to store data. You can interact with them using the following patterns:

1. Access a Box: Use Hive.box<T>(name) to access an existing box of a specific type.
2. Add Data: Use the .add(value) method on a box instance to append data.
3. Read Data: Use the .values property on a box to retrieve all stored items, which can be converted to a list using .toList().

Once configured, you can interact with Hive using boxes. Use Hive.box() to access a box and put(key, value) to store data. Retrieve data using get(key).

import 'package:hive/hive.dart';

final box = Hive.box();
box.put('name', 'David');

final name = box.get('name');
print('Name: $name');

Boxes can be used like lists by using auto-incrementing integer keys.

• box.add(value): Appends a value to the box.
• box.getAt(index): Retrieves a value at a specific index.
• box[index]: Map-style syntax for index-based access.
• box[index] = value: Updates a value at a specific index.

Warning: Index-based operations will throw an error if the index is out of bounds.

final box = Hive.box();

box.add('Rose');
box.add('Tulip');

print(box.getAt(0)); // Rose
print(box[0]); // Rose

box[0] = 'Daffodil';

You can specify a generic type when opening a box to ensure only values of that type are stored.

Note: You must use the same type whenever you access the box. Attempting to open the same box with a different type will result in an error.

final box = Hive.box<String>(name: 'BeeTreasures');
box.put('DaisyDance', 'SweetNectarShake');
// box.put('TulipTango', 777); // This would cause an error

Use box.write() and box.read() to group multiple operations. Transactions are atomic: if an error occurs during a write transaction, none of the changes are applied, ensuring data consistency.

final box = Hive.box();

box.write(() {
  box.store('nectar1', 'GoldenNectar');
  box.store('nectar2', 'WildflowerBrew');
});

box.read(() {
  final val = box.get('nectar1');
});

Hive boxes act as key-value stores (similar to a Map<String, dynamic>). You can insert or update values using .put(), .putAll(), or the map subscript operator [].

• box.put(key, value): Inserts or updates a single key-value pair.
• box.putAll({'key1': val1, 'key2': val2}): Inserts multiple pairs at once.
• box['key'] = value: Map-style syntax for updating/inserting.

final box = Hive.box();
box.put('danceMoves', 'Waggle Dance');
box.put('wingSpeed', 200);
box.putAll({'favoriteFlower': 'Lavender', 'wingSpeed': 210});

// Map syntax
box['danceMoves'] = 'Round Dance';