CODEWITHSUNDEEP
rx-javaobservable
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Reputation: 6073

RxJava search for item in list

I'm trying to turn this into an Observable without having an external variable or extra classes. Is this possible? It's a basic search through a list:

    //...
    for(int i = 0; i < items.size(); i++) {
        if(items.get(i).id == findId) return i;
    }
    return -1;

So basically I have a string id which if I find I'd like to return the item index in the "items" list.

Upvotes: 2

Views: 4671

Answers (3)

Pavel Ilchenko
Pavel Ilchenko

Reputation: 51

I am aware that this is an old question, but maybe someone will come in handy my solution using a helper class. It's a much more flexible, consistent and declarative way to do so. Any finite Observables are supported. Example:

Single<Integer> result = Observable.fromIterable(items)
            .as(IndexedValue.firstMatch(next -> next.id == findId))
            .map(IndexedValue::index)
            .toSingle(-1);

Upvotes: 1

krp
krp

Reputation: 2247

One way to go is to use fromCallable method to create an Observable:

Observable.fromCallable(() -> {
            for(int i = 0; i < items.size(); i++) {
                if(items.get(i).id == findId) return i;
            }
            return -1;
        });

or more declarative approach:

Observable.from(items)
                .filter(item -> item.id == findId)
                .map(items::indexOf);

Upvotes: 1

m.ostroverkhov
m.ostroverkhov

Reputation: 1960

One "neat" way of doing this without additional traverses overhead is as follows: 

  Observable<Integer> index = Observable.from(items)
            .takeWhile(item -> item.id != findId)
            .count()
            .map(count -> count == data.size() ? -1 : count);

But i would stick to non-Rx approach for such simple use cases

Upvotes: 6

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