Publishers.CombineLatest( $indexEndpoint,  validString)
        .flatMap { (indexEndpoint, search)
                              -> AnyPublisher<[Article], Never> in
                self.articles = [Article]()
                return NewsAPI.shared.fetchArticles(from:
                  Endpoint( index: indexEndpoint, text: search )!)
             }
        .assign(to: \.articles, on: self)
        .store(in: &self.cancellableSet)