CODEWITHSUNDEEP
androidrx-javaretrofit2rx-android
Manza
Manza

Reputation: 3527

In what occasion can onNext() be called more than once?

I have defined and interface, with an endpoint that returns JSON. Retrofit converts this JSON into MyObject. It could be also a list, map, etc, it doesn't matter now.

This is how I subscribe.

    subscription = Retrofit.create(MyApi.class)
            .doSomething()
            .subscribeOn(Schedulers.newThread())
            .observeOn(AndroidSchedulers.mainThread())
            .subscribe(new Subscriber<MyObject>() {
                @Override
                public void onCompleted() {
                }

                @Override
                public void onError(Throwable e) {

                }

                @Override
                public void onNext(MyObject myObject) {

                }
            });

My question is:

Is it possible that onNext is called more than once? If yes, in which occasion?

Upvotes: 1

Views: 601

Answers (2)

Abhi Muktheeswarar
Abhi Muktheeswarar

Reputation: 394

If your retrofit returns an array/list of data, onNext is called multiple times. But if your retrofit returns a single data objext, onNext will be called only once. Example:

//POJO 
class User {
int userId;
String UserName;
}

//POJO 
class UserData {
List<User> users;
}

interface RetrofitGithub {
@GET("...")
Observable<List<User>> getUsers(); 

@GET("...")
Observable<UserData> getUserData(); 

}

If you subscribe to getUsers() onNext will be called multiple N times.(N = size of the list)

If you subscribe to getUserData() onNext will be called only once.

Upvotes: 0

Divers
Divers

Reputation: 9569

In your case, no it's impossible, of course if you do not emit more items in doSomething() method.

But there is another, quite usual cases, for instance, if you use Local first approach and subscribing on hot observable which will emit new item each time when data in data base has change.

E.g. using retrofit:

@Override
public Observable<List<FollowMeUser>> getFollowMeUsers() {
    return realm.where(FollowMeUser.class)
            .findAll()
            .asObservable()
            .filter(RealmResults::isLoaded);
}

getFollowMeUsers()
.subscribe(users -> {Timber.d("saved data has changed")}, Timber::e);

Each time when you will insert/modify/delete FollowMeUser collection, all subscribers of getFollowMeUsers will be notified.

Upvotes: 1

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