Summary - Hive

Combine Box, put and TypeAdapter to make a settings store.

Settings store

When building a settings store, you combine box, put and TypeAdapter. First you register an adapter for the Settings class, then open a box and store the settings object. When the app reopens, you read from the box to restore the settings.

Hive.registerAdapter(SettingsAdapter());
final box = await Hive.openBox('app_settings');
await box.put('current', Settings('light'));

Exercise Build a settings store

Define a Settings class (final String theme). Write a SettingsAdapter with typeId 1 and read/write methods. Register the adapter, initialize Hive, open a box named 'app_settings', put Settings('light') under key 'current', retrieve it and print the theme.

Show example solution

import 'package:hive/hive.dart';

class Settings {
  final String theme;
  Settings(this.theme);
}

class SettingsAdapter extends TypeAdapter<Settings> {
  @override
  final int typeId = 1;

  @override
  Settings read(BinaryReader reader) {
    return Settings(reader.readString());
  }

  @override
  void write(BinaryWriter writer, Settings obj) {
    writer.writeString(obj.theme);
  }
}

void main() async {
  Hive.registerAdapter(SettingsAdapter());
  Hive.init('hive_data');
  final box = await Hive.openBox('app_settings');
  await box.put('current', Settings('light'));
  final settings = box.get('current') as Settings;
  print(settings.theme);
  await box.close();
}

Test yourself

When should a TypeAdapter be registered?
- Only on error
- Before opening a box that contains the custom type
- After the box is closed
- At the end of the main function
Show answer

Before opening a box that contains the custom type — The adapter must be registered before opening a box that uses the type; otherwise Hive does not recognize the type.

Adapter read method

Settings read(BinaryReader reader) {
  return Settings(reader.____());
}

Show answer

Settings read(BinaryReader reader) {
  return Settings(reader.readString());
}

Settings store parts

Settings

Settings model
SettingsAdapter

Type converter
'app_settings'

Box name
settings.theme

Stored value

Next lesson: What is Firebase Auth?

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