rx_shared_preferences 1.0.3+2

Shared preferences with RxDart Stream observation. Reactive shared preferences for Flutter. Reactive stream wrapper around SharedPreferences. Lightweight and easy-to-use.

rx_shared_preferences

Author: Petrus Nguyễn Thái Học

• Shared preference with RxDart Stream observation.
• Reactive shared preferences for Flutter.
• Reactive stream wrapper around SharedPreferences.
• This package provides reactive shared preferences interaction with very little code. It is designed specifically to be used with Flutter and Dart.

More detail about returned Observable

• Observable will emit the initial value as its first next event (Emit value as soon as possible after is listen to) (emit null when value is not set)
• It will automatic emit value when value associated with key was changed successfully (emit null when value associated with key was removed or set to null)
• When read value is not valid type (wrong type):
  • Will emit error if value is present (not null)
  • Emit null when value is absent (value is null) (this occurred because null can be cast to any type).
• Can emit two consecutive data events that are equal. You should use Rx operator like distinct (More commonly known as distinctUntilChanged in other Rx implementations) to create an Observable where data events are skipped if they are equal to the previous data event.

Getting Started

In your flutter project, add the dependency to your pubspec.yaml

dependencies:
  ...
  rx_shared_preferences: <latest_version>

Usage

1. Import and instance

Import rx_shared_preferences and shared_preferences

import 'package:rx_shared_preferences/rx_shared_preferences.dart';
import 'package:shared_preferences/shared_preferences.dart';

Wrap your SharedPreferences in a RxSharedPreferences.

final rxPrefs = RxSharedPreferences(
  await SharedPreferences.getInstance()
);

or not need keyword await before SharedPreferences.getInstance()

final rxPrefs = RxSharedPreferences(
  SharedPreferences.getInstance()
);

2. Can add a logger

You can add logger optional parameter to RxSharedPreferences constructor. Logger will log messages about operations (such as read, write) and observable values

final rxPrefs = RxSharedPreferences(
  SharedPreferences.getInstance(),
  const DefaultLogger(),
);

You can custom Logger by implements Logger, or extends class LoggerAdapter (with empty implementations)

class MyLogger extends LoggerAdapter {
  const MyLogger();

  @override
  void readValue(Type type, String key, value) {
    // do something
  }
}

final rxPrefs = RxSharedPreferences(
  SharedPreferences.getInstance(),
  const MyLogger(),
);

3. Select observable (stream) and use

• And then, just listen Observable, transform Observable through operators such as (map, flatMap, etc...).

• If you need listen to this Observable many times, you can use broadcast operators such as share, shareValue, publish, publishValue, ...

• Note: RxDart's Observables extends the Stream class:

  • All methods defined on the Stream class exist on RxDart's Observables as well.
  • All Observables can be passed to any API that expects a Dart Stream as an input.
  • Additional important distinctions are documented as part of the Observable class

// Listen
rxPrefs.getStringListObservable('KEY_LIST').listen(print); // [*]

// Broadcast stream
rxPrefs.getStringListObservable('KEY_LIST').share();
rxPrefs.getStringListObservable('KEY_LIST').shareValue();

// Transform stream
rxPrefs.getIntObservable('KEY_INT')
  .map((i) => /* Do something cool */)
  .where((i) => /* Filtering */)
  ...

// must **use same rxPrefs** instance when set value and select stream
rxPrefs.setStringList('KEY_LIST', ['Cool']); // [*] will print ['Cool']

• In the previous example we re-used the RxSharedPreferences object rxPrefs for set operations. All set operations must go through this object in order to correctly notify subscribers.

• In flutter, you:

  • Can create global RxSharedPreferences instance.
  • Can use InheritedWidget/Provider to provide a RxSharedPreferences instance (create it in main function) for all widgets (recommended). See example/main, example/provider.

rxPrefs1.getStringListObservable('KEY_LIST').listen(print); // [*]

rxPrefs2.setStringList('KEY_LIST', ['Cool']); // [*] will not print anything

The previous example is wrong using way.

4. Get and set methods like to SharedPreferences

RxSharedPreferences is like to SharedPreferences, it provides read, write functions:

-  Future<bool> containsKey(String key);
-  Future<dynamic> get(String key);
-  Future<bool> getBool(String key);
-  Future<double> getDouble(String key);
-  Future<int> getInt(String key);
-  Future<Set<String>> getKeys();
-  Future<String> getString(String key);
-  Future<List<String>> getStringList(String key);

-  Future<bool> clear();
-  Future<void> reload();
-  Future<bool> commit();
-  Future<bool> remove(String key);
-  Future<bool> setBool(String key, bool value);
-  Future<bool> setDouble(String key, double value);
-  Future<bool> setInt(String key, int value);
-  Future<bool> setString(String key, String value);
-  Future<bool> setStringList(String key, List<String> value);

5. Dispose RxSharedPreferences

You can dispose RxSharedPreferences when is no longer needed. Just call rxPrefs.dispose(). Usually you call this method on dispose of a State

Example demo:

1. Build ListView from Stream using RxSharedPreferences

Demo	Code

2. Change theme and locale (language) runtime

License

MIT License

Copyright (c) 2019 Petrus Nguyễn Thái Học

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.