watch method

@Deprecated('Use implicit signal tracking in SignalWidget/SignalStatefulWidget, or localized builders like SignalBuilder/Watch instead.') T watch(BuildContext context, { String? debugLabel, })

Rebuild the Element that the current signal is inside of.

Implementation

@Deprecated(
  'Use implicit signal tracking in SignalWidget/SignalStatefulWidget, or localized builders like SignalBuilder/Watch instead.',
)
T watch(
  BuildContext context, {
  String? debugLabel,
}) {
  if (onSignalRead != null) {
    onSignalRead!(this);
    return peek();
  }

  // 1. If context is our custom SignalElement/SignalStatefulElement, delegate to it
  if (context is SignalElement) {
    context.watchSignal(this);
    return peek();
  }
  if (context is SignalStatefulElement) {
    context.watchSignal(this);
    return peek();
  }

  // 2. If context is a stateful widget using SignalsMixin, delegate to it
  if (context is StatefulElement) {
    final state = context.state;
    if (state is SignalsMixin) {
      return state.watchSignal(this);
    }
  }

  // 3. For any standard Element (Stateless/Stateful)
  if (context is Element) {
    final element = context;
    final signalId = globalId;

    // Check if we already have an active subscription for this signal on this element
    final subs = _elementSubscriptions[element] ??= [];
    final alreadySubscribed = subs.any((s) => s.signalId == signalId);

    if (!alreadySubscribed) {
      // Create a weak reference to the element to avoid lapsed-listener leaks.
      // The subscription closure will NOT keep the element alive in memory!
      final weakElement = WeakReference(element);

      final dispose = subscribe((_) {
        final el = weakElement.target;
        if (el != null && el.mounted) {
          el.markNeedsBuild();
        }
      });

      // Attach the subscription disposer to the Finalizer. When the element is
      // garbage-collected by the Dart VM, this disposer runs automatically.
      _finalizer.attach(element, dispose, detach: dispose);

      // Track it in our Expando to prevent duplicate subscriptions
      subs.add((signalId: signalId, dispose: dispose));
    }
  }

  // Return the value without subscribing again
  return peek();
}