Setup and features

Bloc Superpowers is a Flutter/Dart package created by Marcelo Glasberg, available on pub.dev since Jan 2026. Click here to visit the package page, and here to see all my 17+ packages in pub.dev.

In pubspec.yaml

dependencies:
  bloc_superpowers: ^1.0.0 # Check the latest version
  flutter_bloc: ^9.1.1 # Check the latest version
  fast_immutable_collections: ^11.1.0 # Optional, if you want to use IList

In your widget tree

Add widget Superpowers near the top of your widget tree, somewhere above your MaterialApp:

Widget build(BuildContext context) {
  return Superpowers(
    ...
    child: MaterialApp(
      ...

Note: Failing to add the Superpowers widget will result in runtime errors when you use isWaiting, isFailed, or getException context extensions. All the rest will still work.

List of features

• context.isWaiting(): Use it to show spinners or loading indicators when a Cubit is loading. No need to add explicit loading states to your Cubits anymore.

• context.isFailed(): Show error messages when a Cubit has failed. No need to add explicit error states and error messages to your Cubits anymore.

• UserException: A Cubit that fails can now just throw exceptions.

• UserExceptionDialog and UserExceptionToast: Widgets that shows an error dialog or toast when a Cubit throws a UserException.

• retry: Easily retry failed Cubit methods.

• checkInternet: Check for internet connectivity before executing Cubit methods.

• nonReentrant: Prevent Cubit methods from being called simultaneously.

• sequential: Queue Cubit method calls and process them one after another, in order.

• fresh: Treat Cubit methods as fresh for some time. Prevent reloading data too often.

• debounce: Debounce Cubit method calls to avoid rapid successive calls.

• throttle: Throttle Cubit method calls to limit how often they can be called.

• catchError: Suppress errors, rethrow them, or wrap them in user-friendly exceptions.

• MixConfig: Create reusable configurations for the mix function.

• MixPreset: Create your own reusable mix functions.

• optimisticCommand: Applying an optimistic state change immediately, then run the command on the server, optionally rolling back and reloading.

• optimisticSync: Update the UI immediately and send the updated value to the server, making sure the server and the UI are eventually consistent.

• optimisticSyncWithPush: Similar to optimisticSync, but resilient to server-pushed updates that may modify the same state this action controls.

• Effect: Class that allows Cubits to emit one-time effects to the UI, such as navigation events, dialogs, toasts. Replaces BlocListener.

• EffectQueue: Class that allows Cubits to emit queued one-time effects to the UI, ensuring they are shown one after the other.