armature_reactive

Lightweight MobX-style reactive primitives — Atom, Reaction, and automatic dependency tracking — for pure Dart. No Flutter dependency; consumed by armature and armature_flutter but usable standalone.

Core primitives

Atom<T>

An observable cell. Reads inside a reaction register the reading reaction as an observer; writes notify every registered observer.

final counter = Atom<int>(0);

counter.value = 1;            // imperative write
print(counter.value);         // imperative read

Reaction

A side-effect that re-runs when any tracked atom changes. Use track() to open a dependency-scope — every atom read inside gets wired as a dependency.

final reaction = Reaction(onInvalidate: () {
  print('dependencies changed');
});

reaction.track(() {
  print(counter.value); // reading inside track → tracked
});

counter.value = 2; // invokes onInvalidate asynchronously

Call reaction.clear() when done — detaches the reaction from all atoms it observed.

Batching

Multiple writes inside startBatch() / endBatch() coalesce into a single invalidation pass. Useful when you want "N writes, 1 reaction fire".

startBatch();
a.value = 1;
b.value = 2;
endBatch();  // reactions observing a or b fire exactly once

Reactions re-run until they stabilise (fixed-point); the iteration cap (ReactiveConfig.maxIterations, default 100) guards against oscillating cycles.

Install

dependencies:
  armature_reactive: ^0.1.0

Learn more

  • armature — feature framework that builds Store / State on top of these primitives.
  • Monorepo README — full architecture and examples.

License

MIT — see LICENSE.

Libraries

armature_reactive