armature

Feature-based application framework with dependency-graph resolution, reactive stores, typed ports (Pipe / Behavior / Slots), and tasks. Pure Dart; pair with armature_flutter for Flutter UI.

Large applications quickly devolve into a web of providers and singletons. armature solves this by giving each feature explicit dependencies, eager store construction, and extension points (ports) that other features plug into without mutual knowledge.

Install

dependencies:
  armature: ^1.0.0
  armature_flutter: ^1.0.0   # if you want the Flutter integration

Quickstart

A self-contained Pure Dart "hello world" with two features composing through a dependency. The Logger feature subscribes to the Counter feature's store and prints every change.

import 'package:armature/armature.dart';

typedef CounterState = ({int value});

class CounterStore extends Store<CounterState> {
  CounterStore() : super(state: (value: 0));
  void increment() => update((s) => (value: s.value + 1));
}

final counterFeature = createFeature(
  name: 'Counter',
  stores: (_) => (counter: CounterStore()),
  exports: (api) => api.own,
);

// A second feature observes the counter through the dependency edge.
final loggerFeature = createFeature(
  name: 'Logger',
  dependsOn: [counterFeature],
)..onStart((api, cleanup) {
  final counter = api.of(counterFeature).counter;
  cleanup.subscribe(
    counter,
    (_, s) => print('counter: ${s.value}'),
    fireImmediately: true,
  );
  counter.increment();
  counter.increment();
});

Future<void> main() async {
  final container = AppContainer(
    features: [counterFeature, loggerFeature],
  );
  await container.start();
  // Logger prints: counter: 0, counter: 1, counter: 2
  await container.stop();
}

For the Flutter integration (ArmatureApp, slot widgets, StoreBuilder/StoreSelector, debug overlay), see armature_flutter.

Core concepts

Features

• createFeature({name, dependsOn, optionalDependsOn, stores, exports, ports}) — the sole constructor. Store / export factories are records-based: (counter: CounterStore(), repo: NotesStore()).
• Lifecycle — disabled → pending → active → back to disabled. Stores are constructed eagerly during start(); only onStart reruns on activation cycles.
• Activation helpers — manualActivation, whenActive(parent), whenInactive(parent), whenAllActive([...]), whenStoreState(...).

Stores

Store<T> wraps reactive state with listeners, async tasks, and structural integration into the feature's scopeApi.

typedef NotesState = ({List<String> items});

class NotesStore extends Store<NotesState> {
  NotesStore() : super(state: (items: const []));

  void add(String text) => update((s) => (items: [...s.items, text]));

  late final persist = createVoidTask(
    fn: () async => await db.write(state.items),
    strategy: TaskStrategy.debounce(Duration(milliseconds: 300)),
  );
}

Ports

Extension points that other features plug into. Three kinds in armature core:

• Pipe<T> — sequential transformation. Each active handler receives the previous value, returns the next.
• Behavior<TBranch, TPayload> — priority-based selection. Active handlers return BehaviorDescriptor(...); highest priority wins.
• Slots (SingleSlot / MultiSlot) — Flutter widgets; live in armature_flutter.

// In owner's ports record:
final themeBehavior = createBehavior<ThemeMode, ThemeData>(name: 'theme');

// In child feature:
nightFeature.useBehavior(layoutFeature.ports.themeBehavior, (api) {
  if (!api.own.night.state.enabled) return null;
  return (branch: ThemeMode.dark, payload: ThemeData.dark());
}, priority: 10);

Tasks

Strategy-backed async operations. strategy: is optional — Store.createTask / createVoidTask default to .queue.

• .queue (default) — FIFO sequential queue.
• .once — blocks concurrent invocations until done.
• .latest — only the most recent input finishes.
• .debounce(duration) — fires once after quiet period.
• .throttle(duration, edge) — rate-limit with leading / trailing edge control.

Lifecycle: task.reset() returns the state to TaskIdle (cancels coalesced callers from .latest / .debounce / .throttle(trailing) with TaskError, drops state writes from any in-flight run, clears the .once cache). Pass autoReset: duration at creation to schedule the same transition automatically after TaskDone / TaskFailed.

Picking TError — the third generic decides which thrown values land in TaskFailed (sticky, observable in UI) vs propagate from await task(...) and revert state to TaskIdle:

TError =	Behaviour	When to use
Exception	Exception subclasses stick; Error propagates	Default for API / IO. Domain failures show in UI; programming bugs surface to the error handler.
domain class (e.g. ApiError)	Only that family sticks	Strongly typed errors; UI pattern-matches on specific cases.
Never	Nothing sticks	Task isn't expected to throw in normal flow — any throw is a bug.
Object	Everything sticks, including bugs	Last resort. Loses the bug-vs-domain distinction.

// Default for API/IO calls.
late final fetchUser = createTask<int, User, Exception>(
  fn: (id) async => api.getUser(id),
);

// Typed exception hierarchy.
late final placeOrder = createTask<OrderRequest, OrderId, OrderError>(
  fn: (req) async => api.placeOrder(req),
);

// Strict — fn shouldn't fail; any throw escalates to the caller.
late final increment = createVoidTask<int, Never>(
  fn: () async => state.value + 1,
);

Error routing

Everything user-actionable reaches ContainerOptions.errorHandler:

What	Error type	source
onStart / activation / handler throw	HandlerError	feature name
Listener throw on featureStatusChanged	ListenerError	feature name
Listener throw on portChanged	ListenerError	'<events>'
Port mis-scoped apply	PortError	feature name
Slot widget build throw	RenderError	feature name

Advanced surface

package:armature/armature.dart exposes the ~25 symbols you need to author features, stores, tasks, and ports. Two extra barrels exist for narrower needs:

import 'package:armature/advanced.dart';   // application-level escape hatch
import 'package:armature/framework.dart';  // sibling-package plumbing

• advanced.dart — handler / listener typedefs (BehaviorHandler, PipeHandler, TaskFn, StateChangeListener, ...), individual TaskStrategy* constructor classes, debug-overlay mirrors (ContainerDebug, FeatureDebugInfo, PortDebugInfo), and LoggerDebugInfo. Reach for it when you need to type-annotate a handler field, build a custom debug overlay, or implement a custom Logger.
• framework.dart — base port hierarchy (Port, AnyPort, PortType, PortSubscription). This is plumbing that armature_flutter and custom Renderer implementations need; application code should not import it — typed APIs (Pipe, Behavior, slot widgets) cover every end-user scenario.

Day-to-day feature / store code only needs armature.dart.

Learn more

• 📖 Documentation site — full guide with mental model, glossary, and a Notes/Todo example that builds out every concept.
• armature_flutter — Flutter integration: ArmatureApp, slot widgets, providers, debug overlay.
• armature_reactive — underlying reactive primitives.
• armature_graph — DAG resolver used for dependency graph.
• examples/armature_example — multi-feature reference app.

License

MIT — see LICENSE.