lazy

DatabaseReference+Publisher.swift

extension DatabaseReference {
    func observeSingleEventPublisher(of eventType: DataEventType) -> AnyPublisher<DataSnapshot, Error> {
        Future<DataSnapshot, Error> { [weak self] completion in
            self?.observeSingleEvent(of: eventType) {
                completion(.success($0))
            }
        }
        .eraseToAnyPublisher()
    }
}