So I have one async operation A
that depends on a second, B
. How do I make B a continuation of A as you would have with the then function Javascript Promises, or with ContinueWith in .NET TPL?
Let's take a scenarion from Android where I have two service endpoints:
Code:
private void loadImage(final ImageView imageView) {
Observable<String> stringObs = getImageUrlAsync();
stringObs.subscribe(new Action1<String> () {
@Override
public void call(String imageUrl) {
// First async operation done
Observable<Bitmap> bitmapObs = getBitmapAsync(imageUrl);
bitmapObs.subscribe(new Action1<Bitmap>() {
@Override
public void call(Bitmap image) {
// second async operation done
imageView.setImageBitmap(image);
}
});
}
});
}
I would like not to have these two operations nested code-wise, but be in a format that reads more like it acts - sequentially.
I've been unable to find anything about continuations with regards to Observables in RxJava/RxAndroid. Can anyone please help?
I think you need API flatMap
eg:
Observable.create(new Observable.OnSubscribe<String>() {
@Override
public void call(Subscriber<? super String> subscriber) {
subscriber.onNext("imageUrl");
}
}).flatMap(new Func1<String, Observable<Bitmap>>() {
@Override
public Observable<Bitmap> call(String imageUrl) {
return getBitmapAsync(imageUrl);
}
}).subscribe(new Action1<Bitmap>() {
@Override
public void call(Bitmap o) {
imageView.setImageBitmap(image);
}
});
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