I'm new to RxJava. I would like to download some data for each TempoAccount entity from given collection and store it all in a map accountsWithProjects. When the code of last onNext(TempoAccount tempoAccount) is completed I'd like to call filterAccountsWithProjects(accountsWithProjects) method. Is there some simple way to achieve it?
private void getProjectsForEachTempoAccount(Collection<TempoAccount> tempoAccounts) {
final Map<TempoAccount, Collection<TempoProject>> accountsWithProjects =
new HashMap<>(tempoAccounts.size());
Observable<TempoAccount> accountsObservable = Observable.from(tempoAccounts);
accountsObservable
.compose(ObservableUtils.applySchedulers())
.subscribe(new ObserverAdapter<TempoAccount>() {
#Override
public void onError(Throwable e) {
view.notifyAboutError(e.getMessage());
}
#Override
public void onNext(TempoAccount tempoAccount) {
jira.requestProjectsInfoForTempoAccount(String.valueOf(tempoAccount.getId()))
.subscribeOn(Schedulers.io())
.observeOn(AndroidSchedulers.mainThread())
.subscribe(new ObserverAdapter<Collection<TempoProject>>() {
#Override
public void onError(Throwable e) {
view.notifyAboutError(e.getMessage());
}
#Override
public void onNext(Collection<TempoProject> projects) {
accountsWithProjects.put(tempoAccount, projects);
}
});
}
#Override
public void onCompleted() {
filterAccountsWithProjects(accountsWithProjects);
}
});
}
Problem: In the code above filterAccountsWithProjects(accountsWithProjects) is fired before all observables from onNext(TempoAccount tempoAccount) are completed.
Edit:
I want to create an Observable of such a type: Observable<Map<TempoAccount, Collection<TempoProject>>.
I have two observables given:
Observable<TempoAccount> accountsObservable = Observable.from(tempoAccounts)
Observable<Collection<TempoProject>> projectsForAccountObservable = jira.requestProjectsInfoForTempoAccount(TempoAccount account)
So my questions is: can I connnect them somehow and create the map having these two observables.
You should use the flatMap() function on your original stream to do the things you are currently doing in the onNext(). Also, you don't need to filter the stream in onComplete(). You could use filter() on the stream itself and deal with the problem in a more "Reactive" way.
Here is an example:
accountsObservable
.compose(ObservableUtils.applySchedulers())
.map(tempoAccount -> new Pair<TempoAccount, Collection<TempoProject>>(tempoAccount, fetchInfoAccountForTempoAccount(tempoAccount)))
.filter(pair -> hasProjects(pair))
.toMap(pair -> pair.first(), pair -> pair.second)
.subscribe(...)
EDIT:
Updated the suggested answer - you get the TempoAccounts, then you map each account to a Pair of account and collection of TempoProjects. You filter the pairs to see if you have any projects and then you use toMap() to create your desired result. Be aware, that to get toMap() working, your observables have to call onComplete() when the end of the stream is reached.
Related
I want to perform tasks in RxJava one by one.
For Example:-
1. Fetch User Ids from Server
2. Fetch Users from server by thier Ids.
I have tried this method
public Observable<List> getUids(){
return Observable.create(emitter -> {
List<String> uids = new ArrayList<>();
//fetchData from server
emitter.onNext(uids);
});
}
public Observable<User> getUser(String uid){
return Observable.create(emitter -> {
User user = new User();
//fetchData user from server
emitter.onNext(user);
});
}
//Executing this code like
getUids().flatMapIterable(ids -> ids)
.flatMap(this::getUser)
.subscribe(new Observer<User>() {
#Override
public void onSubscribe(Disposable d) {
}
#Override
public void onNext(User user) {
print("next "+user.getName());
}
#Override
public void onError(Throwable e) {
print("error "+e.getMessage());
}
#Override
public void onComplete() {
print("complete");
}
});
There are some problems in it
1.this is not calling Subscriber's onComplete() method when all users are fetched.
2.if there is an error in getUser method, app is crashing. with io.reactivex.exceptions.UndeliverableException exception
Can you please tell me where I am mistaking?
Call emitter.onComplete() in your getUids() and getUser(...) Observables and then append .toList() after .flatMap(this::getUser).
Returns a Single that emits a single item, a list composed of all the items emitted by the finite source ObservableSource.
UndeliverableException is a wrapper for the exception that is happening in your .flatMap(this::getUser). I can not help you more with the information that you provided, what is it that you want to happen when an exception is thrown?
I have a chain of calls to internet, database and as result I show collected info to user. Now I have very ugly 3-level nested RxJava stream. I really want to make it smooth and easy to read, but I've stuck really hard.
I already read everything about Map, flatMap, zip, etc. Cant' make things work together.
Code: make api call. Received info put in database subscribing to another stream in onSuccess method of first stream, and in onSuccess method of second stream received from DB info finally shows up to user.
Dat Frankenstein:
disposables.add(modelManager.apiCall()
.subscribeOn(Schedulers.io())
.observeOn(mainThread)
.subscribeWith(new DisposableSingleObserver {
public void onSuccess(ApiResponse apiResponse) {
modelManager.storeInDatabase(apiResponse)
//level 1 nested stream:
disposables.add(modelManager.loadFromDatabas()
.subscribeOn(Schedulers.io())
.observeOn(mainThread)
.subscribeWith(new DisposableSingleObserver{
public void onSuccess(Data data) {
view.showData(data);
}
public void onError(Throwable e) {
}
}));
}
#Override
public void onError(Throwable e) {
}
}));
}
I already read everything about Map, flatMap, zip, etc. Cant' make things work together.
Well, you missed something about flatMap, because this is what it's for ;)
disposables.add(
modelManager.apiCall()
.subscribeOn(Schedulers.io())
.doOnSuccess((apiResponse) -> {
modelManager.storeInDatabase(apiResponse)
})
.flatMap((apiResponse) -> {
modelManager.loadFromDatabase()
})
.observeOn(AndroidSchedulers.mainThread())
.subscribe((data) -> {
view.showData(data);
})
);
But if you use a reactive database layer like Room's LiveData<List<T>> support, then you can actually ditch the modelManager.loadFromDatabase() part.
flatMap means convert the result of one stream into another stream, it is likely what you want.
Because you have an Observable that emits a ApiResponse then you have another "source of Observables" that takes this ApiResponse and gives another Observable that you want to observe on.
So you may likely want something like that:
disposables.add(modelManager.apiCall()
.flatMap(apiResponse -> {
modelManager.storeInDatabase(apiResponse);
return modelManager.loadFromDatabas()
})
.subscribeOn(Schedulers.io())
.observeOn(mainThread)
.subscribeWith(new DisposableSingleObserver {
public void onSuccess(ApiResponse apiResponse) {
view.showData(data);
}
public void onError(Throwable e) {
}
})
I have this code :
getLocationObservable() // ---> async operation that fetches the location.
// Once location is found(or failed to find) it sends it to this filter :
.filter(location -> { // ---> I want to use this location in the the onNext in the end
after finishing some calculation here, I either return 'true' and continue
to the next observable which is a Retrofit server call, or simply
return 'false' and quit.
})
.flatMap(location -> getRetrofitServerCallObservable( location )
.subscribeOn(Schedulers.io())
.observeOn(AndroidSchedulers.mainThread()))
.subscribeOn(Schedulers.io())
.observeOn(AndroidSchedulers.mainThread())
.subscribe(
new Observer<MyCustomResponse>() {
#Override
public void onSubscribe(Disposable d) {
_disposable = d;
}
#Override
public void onNext(MyCustomResponse response) {
// I want to be able to use the `location` object here
}
#Override
public void onError(Throwable e) {
}
#Override
public void onComplete() {
}
});
I want to be able to use the location object from line 3(first observable), in the "onNext" that is trigerred by the second observable.
I can't manage to work it out.. any help would be much appreciated.
Instead of
getRetrofitServerCallObservable( location )
you could map the result to be a Pair (from your favourite library) of the response and the location:
getRetrofitServerCallObservable( location ).map(response -> Pair.create(location, response))
Then, in your onNext, you'd be receiving Pair<Location,MyCustomResponse> instances.
If you don't want to use a Pair class, you could use Object[], but if you do, please don't tell me about it :P
I am getting a Flowable from one method called getAlldata()
and this method will get the data from the server and then modify the data that been returned base on the data that had been stored in the DB.
So the process of this method goes like this:
getdata from the server
doOnNext for each item get the id
get the local data by id.
modify the current item
The problem is:
the result will be return before actully the modification of the data in doOnNext() since getting the local data from the DB is another observable.
Question
how can I delay stream until the other observable that is on doOnNext() completes?
The codes
private Flowable<List<MyModule>> getAlldata() {
return remoteDataSource
.getData().flatMap(data -> Flowable.fromIterable(data))
.doOnNext(new Consumer<MyModule>() {
#Override
public void accept(MyModule singleItem) throws Exception {
localDataSource.getData(singleItem.getId())
.firstElement().toFlowable()
.subscribe(new Consumer<Optional<MyModule>>() {
#Override
public void accept(Optional<MyModule> itemOptional) throws Exception {
if (itemOptional.isPresent()) {
// modify the item
}
}
});
}
})
.distinct()
.sorted(ProductsRepository.this::sortItems)
.toList().toFlowable();
}
Use flatmap operator instead of doOnNext() which get the singleItem as a parameter and throw an observable of the type localdatabase. so now you can map the response instead of making your Observable wait.
Observable<ModuleData> obs = remoteDataSource
.getData().flatMapIterable(data ->data)
.flatMap(singleItem->localDataSource.getData(singleItem.getId()))
.distinct()
.sorted(ProductsRepository.this::sortItems)
.toList().toFlowable();
I am relatively new to RXJava in general (really only started using it with RXJava2), and most documentation I can find tends to be RXJava1; I can usually translate between both now, but the entire Reactive stuff is so big, that it's an overwhelming API with good documentation (when you can find it). I'm trying to streamline my code, an I want to do it with baby steps. The first problem I want to solve is this common pattern I do a lot in my current project:
You have a Request that, if successful, you will use to make a second request.
If either fails, you need to be able to identify which one failed. (mostly to display custom UI alerts).
This is how I usually do it right now:
(omitted the .subscribeOn/observeOn for simplicity)
Single<FirstResponse> first = retrofitService.getSomething();
first
.subscribeWith(
new DisposableSingleObserver<FirstResponse>() {
#Override
public void onSuccess(final FirstResponse firstResponse) {
// If FirstResponse is OK…
Single<SecondResponse> second =
retrofitService
.getSecondResponse(firstResponse.id) //value from 1st
.subscribeWith(
new DisposableSingleObserver<SecondResponse>() {
#Override
public void onSuccess(final SecondResponse secondResponse) {
// we're done with both!
}
#Override
public void onError(final Throwable error) {
//2nd request Failed,
}
});
}
#Override
public void onError(final Throwable error) {
//firstRequest Failed,
}
});
Is there a better way to deal with this in RXJava2?
I've tried flatMap and variations and even a Single.zip or similar, but I'm not sure what the easiest and most common pattern is to deal with this.
In case you're wondering FirstRequest will fetch an actual Token I need in the SecondRequest. Can't make second request without the token.
I would suggest using flat map (And retrolambda if that is an option).
Also you do not need to keep the return value (e.g Single<FirstResponse> first) if you are not doing anything with it.
retrofitService.getSomething()
.flatMap(firstResponse -> retrofitService.getSecondResponse(firstResponse.id)
.subscribeWith(new DisposableSingleObserver<SecondResponse>() {
#Override
public void onSuccess(final SecondResponse secondResponse) {
// we're done with both!
}
#Override
public void onError(final Throwable error) {
// a request request Failed,
}
});
This article helped me think through styles in how I structure RxJava in general. You want your chain to be a list of high level actions if possible so it can be read as a sequence of actions/transformations.
EDIT
Without lambdas you can just use a Func1 for your flatMap. Does the same thing just a lot more boiler-plate code.
retrofitService.getSomething()
.flatMap(new Func1<FirstResponse, Observable<SecondResponse> {
public void Observable<SecondResponse> call(FirstResponse firstResponse) {
return retrofitService.getSecondResponse(firstResponse.id)
}
})
.subscribeWith(new DisposableSingleObserver<SecondResponse>() {
#Override
public void onSuccess(final SecondResponse secondResponse) {
// we're done with both!
}
#Override
public void onError(final Throwable error) {
// a request request Failed,
}
});
Does this not work for you?
retrofitService
.getSomething()
.flatMap(firstResponse -> retrofitService.getSecondResponse(firstResponse.id))
.doOnNext(secondResponse -> {/* both requests succeeded */})
/* do more stuff with the response, or just subscribe */