Note

• If a class mixed in with LocalFilePrefMixin, then it can be used as ValueNotifier. LocalFilePrevMixin implements all ValueNotifier methods with internal ValueNotifier delegate.

Usage

1. Register global Storage

Storage is content provider of your local file.

We provide SharedPreferencesStorage class.

You can use it like that in the very first of application bootstrap.

⚠️Run registerGlobalStorage before any usage of LocalFilePrefMixin

import 'package:local_file_preferences/local_file_preferences.dart';

void main() async {
  var sharedPreferences = await SharedPreferences.getInstance();
  registerGlobalStorage(
    SharedPreferencesStorage(sharedPreferences: sharedPreferences)
  );
}

Or you can create your own local file content provider by implementing Storage directly.

class MyStorage implements Storage {
  @override
  String? getString(String key) {
    ...
  }

  @override
  Future<void> setString(String key, String value) {
    ...
  }
}

Storage interface is simple to implement.

2. Mix in your class with LocalFilePrefMixin

For example,

class L10NSettings with LocalFilePrefMixin<L10NSettingsValue>

There are methods must be implement.

T get fallback

Provide your data fallback for when mixin can't load local file(maybe first install).

String get fileName

The file name of preferences file in the local file system.

e.g.) my_data.dat

Map<String, dynamic> toJson()

Provide convert method from your data to json.

T fromJson(Map<String, dynamic> json)

Provide convert method from json to your data.

storage (Optional)

Provide storage if you need differentiate local file content provider.

The default storage is set by registerGlobalStorage.

Example

enum L10NSettingsValue {
  enUS(Locale('en', 'US')),
  ko(Locale('ko')),
  ;

  final Locale locale;
  const L10NSettingsValue(this.locale);
}

class L10NSettings with LocalFilePrefMixin<L10NSettingsValue> {
  @override
  L10NSettingsValue get fallback =>
      Intl.getCurrentLocale().startsWith('en') ? L10NSettingsValue.enUS : L10NSettingsValue.ko;

  @override
  String get fileName => 'L10N_settings.dat';

  @override
  Json toJson() => {'locale': value.name};

  @override
  L10NSettingsValue fromJson(Json json) =>
      L10NSettingsValue.values.firstWhereOrNull((element) => element.name == json['locale']) ??
      L10NSettingsValue.enUS;
}

3. LocalFilePrefMixin API

T value

Value of your data(getter, setter).

ValueNotifier<T> data

The ValueNotifier wrapper of your data.

T load()

Load your data from local file. This can be returnned null if there is no saved local file.

This is called at first of initialization automatically.

Futuer<void> save()

Save current data to local file

void scheduleSave()

Schedule save with throttling(2 seconds).

This is useful for situation that you should save intensively.