smf_shared_preferences 0.4.0

The SMF module of preferences with shared_preferences for the Flutter app that SMF generates. It remembers the settings of the app that are no secret, such as the theme mode.

example/README.md

Generate a Flutter app that remembers its settings

shared_preferences is the module of the SMF CLI with which the app remembers its settings that are no secret between its launches. Choose it with -m:

dart pub global activate smf_flutter_cli
smf create my_app -m shared_preferences --no-input

The module adds shared_preferences to the pubspec.yaml of the app, and lib/core/preferences/shared_app_preferences.dart with the preferences on SharedPreferencesWithCache. The rest of the app uses the interface in lib/core/preferences/app_preferences.dart, which the preferences role adds: AppPreferences has a read and a write for a String, a bool, an int, a double and a List<String>, such as getString(key) and setString(key, value), and remove(key).

bootstrap() opens the preferences before the first frame and gives them to each function of _restorers in lib/core/preferences/app_preferences.dart. Code of the app gets the preferences there. To remember a setting, write such a function and add it to that list. It reads the setting into the state that the widgets listen to, and keeps the preferences for the writes. This one is in a file of lib/features/reader/:

import 'package:flutter/foundation.dart';

import '../../core/preferences/app_preferences.dart';

/// The font size of the reader, which its widgets listen to.
final readerFontSize = ValueNotifier<double>(16);

AppPreferences? _preferences;

/// Restores the font size from the preferences, and keeps them.
void restoreReaderFontSize(AppPreferences preferences) {
  _preferences = preferences;
  readerFontSize.value =
      preferences.getDouble('reader.font_size') ?? readerFontSize.value;
}

/// Changes the font size, and saves it.
Future<void> setReaderFontSize(double size) async {
  readerFontSize.value = size;
  await _preferences?.setDouble('reader.font_size', size);
}

A read is synchronous, and returns null when the key has no value of its type.

A number is read only as the type that it was saved as: after setInt('reader.font_size', 18), getDouble('reader.font_size') returns null, and getInt returns null for a key with a double, even a whole number such as 18.0. So save and read a setting as one type.

shared_preferences keeps the values in DataStore on Android and in UserDefaults on iOS. Neither is encrypted, and a backup of the device carries them, so never store a token, a password, an API key or an encryption key in the preferences.

With a module of dependency injection, such as get_it, the preferences are registered in the container, and a feature takes them with resolve in its composition file.

Without -m, smf create asks which module provides the preferences of the app.

The documentation has more on the shared_preferences module.