How to make N-number of requests and send their result to the server [RXjava]?

Question

Java

Request to create tags = N (any) number of requests for the same thing, for example, create a tag (the request returns the created tag with an ID)
Saving a list of tags to the user = One request in which you need to fit a list of results from tags (list of IDs)

How to implement it correctly such an idea in RXjava?

Answer 1

If I understand the question correctly, then something like this.

Single<Long> createTag(String tag) {
// creating tag, returning long id
}

Single<List<Long>> createTags(List<String> tags) {
    return Observable.fromIterable(tags)
        .flatMap(this::createTag)
        .toList();
}

Completable attachTagsToUser(List<String> tags, User user) {
    return createTags(tags)
        .flatMapCompletable(tagIds -> /* do what you want, here the ids */);
}