Flutter Pagination Fix With async* Has Concurrency Flaws, BlocSignal Offers Alternative

Mobile developer Ali Wajdan proposed using Dart async* generators and StreamIterator to solve the common infinite scroll race condition in Flutter apps, where rapid scroll events trigger duplicate network requests and broken state. While the approach moves mutable state like page counters and loading flags inside the generator, critics point out it does not eliminate the need for a manual concurrency guard. Dart's StreamIterator.moveNext() is not concurrency-safe and throws a runtime error if called again before a previous request resolves, a limitation Wajdan himself acknowledged. The iterator also lacks built-in support for reactive UI states such as error handling, pull-to-refresh, and bottom loading indicators, requiring developers to maintain an external state container regardless. A pattern called BlocSignal has been proposed as a more complete architectural solution to address these remaining concurrency and state management gaps.