watchItem<T extends StorableModel> method

Future<Stream<T?>> watchItem<T extends StorableModel>(String tag, String id, T fromJson(Map<String, dynamic>))

Watches for changes to a specific item in the data store.

This method loads the initial data for the provided tag, adds it to the stream controller, and returns a Stream that emits an object of type T whenever the specified item changes. If the item does not exist, null is emitted. The transformation is performed using the provided fromJson function.

Type Parameters:

• T: A type extending StorableModel that represents the model of the data.

Parameters:

• tag: A String representing the category or group of data to monitor.
• id: A String representing the unique identifier of the item to watch.
• fromJson: A function that converts a Map<String, dynamic> to an object of type T.

Returns:

• A Future<Stream<T?>> that emits the updated item of type T or null if not found.

Throws:

• Any errors encountered during the initial data load will propagate.

Implementation

Future<Stream<T?>> watchItem<T extends StorableModel>(
  final String tag,
  final String id,
  final T Function(Map<String, dynamic>) fromJson,
) async {
  // Initial load
  await _loadData(tag).then((final Map<String, dynamic> data) {
    _getController(tag).add(data);
  });

  return _getController(tag).stream.map((final Map<String, dynamic> data) {
    final dynamic itemData = data[id];
    if (itemData == null) {
      return null;
    }
    return fromJson(itemData as Map<String, dynamic>);
  });
}