java - RxJava 两个请求按顺序

Question

我有两个请求，第二个请求依赖于第一个请求，那么如何按顺序进行请求，因为如果并行请求，有一些检查将收到 null

        Observable<Map<Integer, SupportedVersion>> supportedVersionObservable = contentAPI
            .getSupportedVersionsContent()
            .compose(ReactiveUtils.applySchedulers())
            .map(supportedVersionsContentContentContainer -> supportedVersionsContentContentContainer.getContent().get(0).getMessage())
            .doOnNext(supportedVersionsMap -> {
                Timber.i("doOnNext invoked from supported version observable");
                for (Map.Entry<Integer,SupportedVersion> entry : supportedVersionsMap.entrySet())
                    if (Build.VERSION.SDK_INT >= entry.getKey())
                        model.setSupportedVersion(entry.getValue());

                model.setCurrentVersionExpiryDate(model.getSupportedVersion().getCurrentVersionExpiryDate());

                if (model.getSupportedVersion() != null)
                    model.setNewFeaturesSeen(sharedPreferencesManager.isNewFeaturesSeen(model.getSupportedVersion().getAvailableVersions().get(0)));
                if (model.isNewFeaturesSeen());
                //request data from here 
            })
            .retry(1);

    Observable<List<WhatsNew>> getWhatsNewFeature = contentAPI
            .getWhatsNewFeature(model.getSupportedVersion().getAvailableVersions().get(0))
            .compose(ReactiveUtils.applySchedulers())
            .doOnNext(whatsNewList -> {
                Timber.i("doOnNext invoked from supported version observable");
                if (!whatsNewList.isEmpty())
                    model.setWhatsNews(whatsNewList);
            })
            .retry(1);

Answer 1

您可以使用 flatMap 来实现:

public Observable<List<WhatsNew>> makeRequest { 
   return contentAPI
        .getSupportedVersionsContent()
        .flatMap(supportedVersionsMap -> {
             //... model initialization
             return contentAPI
                    .getWhatsNewFeature(model.getSupportedVersion().getAvailableVersions().get(0))
                    .compose(ReactiveUtils.applySchedulers())
                    .doOnNext(whatsNewList -> {
                    Timber.i("doOnNext invoked from supported version observable");
                    if (!whatsNewList.isEmpty())
                        model.setWhatsNews(whatsNewList);
                    })
                   .retry(1);
        });