remember<T extends Object> method

T remember<T extends Object>({ T factory()?, T factory2(Lifecycle)?, FutureOr<void> onDispose(T)?, Object? key, })

以当前context、类型T和key为索引 记住该对象，并且以后将再次返回该对象

• factory 和 factory2 如何构建这个对象，不能同时为空, factory 优先级高于 factory2
• onDispose 定义销毁时如何处理，一定晚于context的dispose,非常注意不可使用context相关内容

Implementation

T remember<T extends Object>({
  T Function()? factory,
  T Function(Lifecycle)? factory2,
  FutureOr<void> Function(T)? onDispose,
  Object? key,
}) {
  if (factory == null && factory2 == null) {
    throw 'factory and factory2 cannot be null at the same time';
  }

  final lifecycle = Lifecycle.of(this);
  final managers = lifecycle.extData.getOrPut<
          Map<BuildContext, _RememberDisposeObserver>>(
      key: _keyRemember,
      ifAbsent: (l) {
        final result =
            WeakHashMap<BuildContext, _RememberDisposeObserver>.identity();

        /// 不持有 Map，防止内存泄漏
        lifecycle.addLifecycleObserver(MapAutoClearObserver(result));
        return result;
      });

  final manager = managers.putIfAbsent(
      this, () => _RememberDisposeObserver._(this, lifecycle));

  return manager.getOrCreate<T>(factory, factory2, onDispose, key);
}