addService<Id, Data> method

@protected Service<Id, Data> addService<Id, Data>(WebSocketsService service)

Keeps service, which close closes, as a Service of Id and Data.

Throws an ArgumentError if Data is not nullable: the methods of a WebSocketsService return null, as their results come as events.

Implementation

@protected
Service<Id, Data> addService<Id, Data>(WebSocketsService service) {
  if (service is! Service<Id, Data>) {
    throw ArgumentError(
      'The data of a WebSocket service is given as events, and its methods '
      'return null, so its type must be nullable: use '
      'service<$Id, $Data?>(...), not service<$Id, $Data>(...).',
    );
  }
  _services.add(service);
  return service as Service<Id, Data>;
}