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rodydavis/signals.dart ★9999⑂99

Type: SignalBuilder

API reference and details for SignalBuilder from signals.dart.

SignalBuilder#

Kind: class  |  Package: package:signals_flutter

Class: SignalBuilder#

A premium, surgical builder widget that rebuilds locally on signal changes.

SignalBuilder tracks any signals read dynamically within its builder callback and automatically subscribes to them. When any of these signals update, only the SignalBuilder is rebuilt, preventing costly rebuilds of the surrounding widget subtree.

This widget provides predictable, immediate, and memory-safe subscription management, automatically tearing down all active signal subscriptions when the builder is unmounted.

Surgical Counter Example#

final count = signal(0);

class CounterPage extends StatelessWidget {
  const CounterPage({super.key});

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: const Text('Counter')),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: [
            const Text('This static text never rebuilds!'),
            const SizedBox(height: 20),
            // Only this specific Text widget rebuilds when 'count' changes:
            SignalBuilder(
              builder: (context) => Text(
                'Count: ${count.value}',
                style: Theme.of(context).textTheme.headlineMedium,
              ),
            ),
          ],
        ),
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: () => count.value++,
        child: const Icon(Icons.add),
      ),
    );
  }
}

Tip

Keep SignalBuilder widgets as small and leaf-level as possible in your tree to maximize rendering performance.

Members of SignalBuilder#

Member Type Signature Description
SignalBuilder constructor dart SignalBuilder({super.key, required this.builder, this.dependencies = const []}) Creates a SignalBuilder widget.
builder field dart Widget Function(BuildContext context) builder The widget to rebuild when any signals change.
dependencies field dart List<core.ReadonlySignal> dependencies List of optional dependencies to watch.
build method dart Widget build(BuildContext context)

References#

The SignalBuilder type is referenced and used in the following pages: