My current Android Application employs Retrofit
and RxJava
to choreograph my network calls.
I have modelled my HTTP GET(s) as Single<Response<String>>
and POST(s) as Completable
.
The sequence of calls that I require are as follows:-
Sequentially call GET(1), GET(2), GET(3)
Parallel call POST(1), POST(2)
When both POST(1) & POST(2) have completed OK, call GET(4).
I have a partial solution. I have coded calls for the the First three GET(s)
followed by the POST calls
My code resembles this:-
Single.concat(getRequests())
.subscribeOn(Schedulers.single())
.doOnError(throwable -> Log.e(TAG, "Manage Totals Failed", throwable))
.doFinally(new Action() {
@Override
public void run() throws Exception {
manageExecutions(combineExecutions());
}
})
.subscribe();
/**
* @return
*/
private static Iterable<Single<Response<String>>> getRequests() {
final API_CALL_GET[] apiCalls = API_CALL_GET.values();
final List<Single<Response<String>>> requests = new ArrayList<>(apiCalls.length);
for (final API_CALL_GET apiCall : apiCalls) {
requests.add(apiCall.request());
}
return requests;
}
public enum API_CALL_GET {
GET_ONE {
@Override
public Single<Response<String>> request() {
return RETRO_SERVICE
.getOne(authToken, new HashMap<>())
.doAfterSuccess(this::persistDataOne)
.doOnError(error -> ever(error));
}
}, GET_TWO {
@Override
public Single<Response<String>> request() {
return RETRO_SERVICE
.getTwo(authToken, new HashMap<>())
.doAfterSuccess(this::persistDataTwo)
.doOnError(error -> ever(error));
}
},
GET_THREE {
@Override
public Single<Response<String>> request() {
return RETRO_SERVICE
.getThree(authToken, new HashMap<>())
.doAfterSuccess(this::persistDataThree)
.doOnError(error -> ever(error));
}
};
public abstract Single<Response<String>> request();
}
private static Action manageExecutions(final List<Completable> completables) {
return new Action() {
@Override
public void run() throws Exception {
Completable
.concat(completables)
.subscribeOn(Schedulers.io())
.doOnError(throwable -> Log.e(TAG, "Manage Totals Failed", throwable))
.doOnComplete(new Action() {
@Override
public void run() throws Exception {
accumulateAmounts();
}
})
.subscribe();
}
};
}
/**
* @return
*/
private static List<Completable> combineExecutions() {
final API_CALL_POST[] apiCalls = API_CALL_POST.values();
final List<Completable> requests = new ArrayList<>(apiCalls.length);
for (final API_CALL_POST apiCall : apiCalls) {
requests.addAll(apiCall.requests());
}
return Lists.newArrayList(Iterables.unmodifiableIterable(requests));
}
public enum API_CALL_POST {
POST_ONE {
@Override
public List<Completable> requests() {
return NetworkController.postRecommenderExecutions();
}
},
POST_TWO {
@Override
public List<Completable> requests() {
return NetworkController.postSavedSearcheExecutions();
}
};
public abstract List<Completable> requests();
}
public static List<Completable> postONE() {
final List<Completable> completables = new ArrayList<>();
final List<OneDO> oneDOS = fetchOnes();
for (final OneDO oneDO : oneDOS) {
completables.add(RETRO_SERVICE.runCompletableOnes(authToken, oneDO.getId())
.doOnError(new Consumer<Throwable>() {
@Override
public void accept(final Throwable throwable) throws Exception {
Log.e(TAG, "accept: ", throwable);
}
}));
}
return completables;
}
public static List<Completable> postTWO() {
final List<Completable> completables = new ArrayList<>();
final List<TwoDO> twoDOS = fetchTwos();
for (final TwoDO twoDO : twoDOS) {
completables.add(RETRO_SERVICE.runCompletableTwos(authToken, twoDO.getId())
.doOnError(new Consumer<Throwable>() {
@Override
public void accept(final Throwable throwable) throws Exception {
Log.e(TAG, "accept: ", throwable);
}
}));
}
return completables;
}
What I am having difficulty with is correctly chaining my calls
e.g. I thought I would be able to develop a solution that resembled this pseudo code
Single.concat(GET_1… GET_N).onComplete(POST_1… POST_N).onComplete(GET_LAST)
however my current partial solution only calls the First group of GET(s) followed by the POST(s) and the GET and POST calls are not “chained”
I cannot see how to create a chain of calls that support my use case.
Is it possible to combine Single
-> Completable
-> Single
in a chained call?
UPDATE
Based on Daniil answer I ended up with this solution:-
Single.concat(getRequests())
.subscribeOn(Schedulers.io())
.doOnError(throwable -> Log.e(TAG, "accept[0000]: ", throwable))
.ignoreElements()
.andThen(Completable.merge(combineExecutions()))
.doOnError(throwable -> Log.e(TAG, "accept: ", throwable))
.doOnComplete(() -> Controller.accumulateTotals())
.subscribe();
In kotlin it would look something like this:
fun generateGetRequests(): List<Single<Response<String>>> {
return listOf(retrofit.firstGet(), retrofit.secondGet(), ... ,retrofit.lastGet())
}
fun generatePostRequests(): List<Completable> {
return listOf(retrofit.firstPost(), ..., retrofit.lastPost())
}
fun doSomethingWithResponses(responses: Array<Any>) {
// Do Something, like save to db
}
fun runRequests() {
Single.zip(generateGetRequests(), { responses ->
doSomethingWithResponses(responses)
}).ignoreElements()
.andThen(Completable.merge(generatePostRequests()))
.subscribeOn(Schedulers.io())
.subscribe()
}
Answer:
Chaining up different types can happen either by converting them onto a shared reactive type (such as Observable
) and concatenating, or using one of the continuation approaches via flatMapX
and andThen
:
someSingle
.flatMapCompletable(result1 -> {
sideEffect(result1);
return someCompletable;
})
.andThen(Single.defer(() -> {
sideEffectAfterCompletable();
return someOtherSingle;
}))
...
Tags: android, androidjava