dart mixin for locally caching state

cached_state.dart

import 'package:flutter/foundation.dart';
import 'package:hive_flutter/adapters.dart';

mixin CachedState<State, CachedType> {
  
  ///Function for serializing data from [State] to a more useable [CachedType]
  ///that can be stored easily by [Hive]
  CachedType toCacheData();

  ///Function for serializing data from [CachedType] to a more useable [State]
  State fromCachedData(CachedType data);

  ///State Key:
  ///
  ///this is the key that will be used to uniquely identify this state from others
  ///it must be overriden to avoid errors
  String? key;
  
  ///Cache Key getter:
  ///
  ///this is returns the current State's cache Key or a default value
  ///note that this default value is equal to "Type || Type"
  ///Do well to override [key]
  String get cacheKey {
    return key ?? '${State.runtimeType} || ${CachedType.runtimeType}';
  }

  String get _cacheDataKey => '$cacheKey-cacheData';

  bool cacheInitialized = false;

  @protected
  Future<void> initializeCache() async {
    assert(!cacheInitialized, 'Has already been initialized');
    cacheInitialized = true;
    _cacheBox = await Hive.openBox<CachedType>(cacheKey);
  }

  Stream<BoxEvent> get cacheChanges {
    assert(cacheInitialized, 'Must Be Initialized First');
    return _cacheBox.watch();
  }

  late final Box<CachedType> _cacheBox;

  void close() {
    _cacheBox.close();
    cacheInitialized = false;
  }

  State? fetchCache() {
    assert(cacheInitialized, 'Must Be Initialized First');
    CachedType? data = _cacheBox.get(_cacheDataKey);
    State? state = data == null ? null : fromCachedData(data);
    return state;
  }

  Future<void> clearCache() async {
    assert(cacheInitialized, 'Must Be Initialized First');
    await _cacheBox.clear();
  }

  Future<void> saveCache() async {
    assert(cacheInitialized, 'Must Be Initialized First');
    CachedType cacheData = toCacheData();
    await _cacheBox.put(_cacheDataKey, cacheData);
  }
}

Nice !!