grab method

R grab(BuildContext context)

Returns the value of the ValueListenable that this method was called on, and starts listening for changes in the ValueListenable to rebuild the widget associated with the provided BuildContext when there is a change in the value of the ValueListenable.

A Grab is necessary as an ancestor of the widget this method is used for. GrabMissingError is thrown otherwise.

void main() {
  runApp(
    const Grab(child: ...),
  );
}

class Item {
  Item({required this.name, required this.quantity});

  final String name;
  final int quantity;
}

final notifier = ValueNotifier(
  Item(name: 'Milk', quantity: 3),
);

...

class InventoryItem extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    final item = notifier.grab(context);
    return Text(item.name);
  }
}

Implementation

R grab(BuildContext context) {
  return grabAt(context, (value) => value);
}