Getting started

JIntent is a Flutter library for explicit intents, immutable state and one-time UI effects. Controllers manage state; intents perform operations; effect handlers present dialogs, navigation and feedback outside persistent state.

Read the interactive guide (English and Spanish) for the concepts, live demos and the API reference.

Installation

flutter pub add jintent

Or declare it yourself. Version 3.0.0 requires Flutter 3.29.2 or newer:

dependencies:
  jintent: ^3.0.0

Import the public entry point:

import 'package:jintent/jintent.dart';

Optional pieces have their own entry points, so the core stays small:

Import	Contents
package:jintent/jintent.dart	State, intents, controller, effects, dispatchers, JObserver, Either, use cases, mappers
package:jintent/devtools.dart	Structured logging, correlation, metrics, debug overlay
package:jintent/testing.dart	State and effect recorders, global reset
package:jintent/widgets.dart	Controller builder and selector without a provider package
package:jintent/undo_redo.dart	Stable undo/redo, observable history and commands
package:jintent/navigation.dart	Thin Navigator abstraction
package:jintent/utils.dart	Throttler, validation, color and platform helpers

See undo and redo for local edit history, UI integration, ordering and migration from the legacy experimental import.

Upgrading from 2.x changes state equality, effect failures and disposal behavior. Review the migration guide first.

What’s new in 3.0.0

• Entry points: jintent.dart holds only the core; devtools, undo/redo, widgets, navigation, utilities and test helpers moved to their own imports.
• Predictable state: updates equal to the current state are skipped, so listeners and observers only see real changes.
• Safer effects: an awaited effect without a listener or handler fails with StateError, and disposal fails pending results. Effect buffering is opt-in.
• Concurrency: droppable and restartable dispatchers, with cooperative cancellation through JIntent.cancel.
• Observability: composable JObserverDelegates that also report failed, cancelled and dropped intents, plus richer metrics and overlay.
• Also new: stable undo/redo with observable history, JControllerBuilder and JControllerSelector, and test recorders in package:jintent/testing.dart.

Several of these change behavior compared with 2.x. See the full changelog and the migration guide.

Minimal example

import 'package:jintent/jintent.dart';

class CounterState extends JState {
  final int count;
  const CounterState({this.count = 0});

  @override
  CounterState copyWith({int? count}) =>
      CounterState(count: count ?? this.count);

  @override
  List<Object?> get props => [count];
}

class IncrementIntent extends JIntent<CounterState>
    with JIntentHelpers<CounterState> {
  @override
  Future<void> onInvoke() async {
    update((state) => state.copyWith(count: state.count + 1));
  }
}

class CounterController extends JController<CounterState> {
  CounterController() : super(const CounterState());

  Future<void> increment() => intent(IncrementIntent());

  @override
  void onInit() {}
}

Future<void> main() async {
  final controller = CounterController();
  try {
    await controller.increment();
    print(controller.currentState.count); // 1
  } finally {
    controller.dispose();
  }
}

Connect the controller directly with JControllerBuilder or JControllerSelector from package:jintent/widgets.dart, or use your StateNotifier integration. The widget guide covers ownership, controller replacement and selecting part of a state. The example gallery uses the builders in its four focused labs and Riverpod with JEffectListener in the counter.

Contracts

• JState: include relevant values in props; return new immutable states. Updates equal to the current state are skipped.
• JIntent: override onInvoke and await its work. One instance cannot run concurrently; it can be reused after completion.
• JController: dispatches sequentially by default. Return dispatch futures and handle their errors at the UI boundary. onInit runs synchronously from the base constructor, before the subclass constructor body. Pass effectBufferSize to retain effects emitted before the UI attaches.
• JEffect: transient UI events. Register each concrete effect type in a JSideEffectHandler and complete awaited results. A subscription alone does not guarantee completion; configure a timeout for awaited UI work.
• JObserver: register JObserverDelegates to observe intents (including failures), state and effects; see observability.
• Disposal rejects queued intents and pending effect results; running service calls and handlers need their own cancellation or lifecycle checks.

See effects for registration, failures and timeouts, and error handling for operation boundaries.