Refactor (#3)

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* Update pubspec.yaml

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* add options

Author: hoc081098

analysis_options.yaml

@@ -1,4 +1,8 @@
 include: package:pedantic/analysis_options.1.9.0.yaml
+analyzer:
+  strong-mode:
+    implicit-casts: false
+    implicit-dynamic: false
 linter:
   rules:
     - public_member_api_docs

lib/rx_storage.dart

@@ -3,6 +3,7 @@
 /// More dartdocs go here.
 library rx_storage;
 
+export 'src/impl/real_storage.dart';
 export 'src/interface/rx_storage.dart';
 export 'src/interface/storage.dart';
 export 'src/logger/default_logger.dart';

lib/src/async_memoizer.dart

@@ -0,0 +1,46 @@
+// Copyright (c) 2015, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+import 'dart:async';
+
+/// A class for running an asynchronous function exactly once and caching its
+/// result.
+///
+/// An `AsyncMemoizer` is used when some function may be run multiple times in
+/// order to get its result, but it only actually needs to be run once for its
+/// effect. To memoize the result of an async function, you can create a
+/// memoizer outside the function (for example as an instance field if you want
+/// to memoize the result of a method), and then wrap the function's body in a
+/// call to [runOnce].
+///
+/// This is useful for methods like `close()` and getters that need to do
+/// asynchronous work. For example:
+///
+/// ```dart
+/// class SomeResource {
+///   final _closeMemo = AsyncMemoizer();
+///
+///   Future close() => _closeMemo.runOnce(() {
+///     // ...
+///   });
+/// }
+/// ```
+class AsyncMemoizer<T> {
+  /// The future containing the method's result.
+  ///
+  /// This can be accessed at any time, and will fire once [runOnce] is called.
+  Future<T> get future => _completer.future;
+  final _completer = Completer<T>();
+
+  /// Whether [runOnce] has been called yet.
+  bool get hasRun => _completer.isCompleted;
+
+  /// Runs the function, [computation], if it hasn't been run before.
+  ///
+  /// If [runOnce] has already been called, this returns the original result.
+  Future<T> runOnce(FutureOr<T> Function() computation) {
+    if (!hasRun) _completer.complete(Future.sync(computation));
+    return future;
+  }
+}