class Resource<T> {
  final T? data;
  final bool isLoading;
  final Exception? error;

  Resource({this.data, this.isLoading = false, this.error});

  static const _unset = Object();

  Resource<T> copyWith({T? data, bool? isLoading, Object? error = _unset}) {
    return Resource<T>(
      data: data ?? this.data,
      isLoading: isLoading ?? this.isLoading,
      // Distinguish "not provided" from an explicit null to allow clearing error.
      error: error == _unset ? this.error : error as Exception?,
    );
  }
}