flatZip in RxJava

问题

I'm zipping multiple Observables together and then transforming them in a way that results in an Observable:

final Observable<Observable<M>> result = Observable.zip(obs1, obs2, transformFunc);

What I'd like to be able to do is:

final Observable<M> result = Observable.flatZip(obs1, obs2, transformFunc);

What's the cleanest way to do this, given flatZip doesn't exist (maybe I should submit one). At the moment I'm having to flatMap the result in on itself.

回答1:

public class RxHelper {

    public static <T1, T2, R> Observable<R> flatZip(Observable<? extends T1> o1, Observable<? extends T2> o2, final Func2<? super T1, ? super T2, Observable<? extends R>> zipFunction) {
        return Observable.merge(Observable.zip(o1, o2, zipFunction));
    }

    public static <T1, T2, T3, R> Observable<R> flatZip(Observable<? extends T1> o1, Observable<? extends T2> o2, Observable<? extends T3> o3, Func3<? super T1, ? super T2, ? super T3, Observable<? extends R>> zipFunction) {
        return Observable.merge(Observable.zip(o1, o2, o3, zipFunction));
    }

    public static <T1, T2, T3, T4, R> Observable<R> flatZip(Observable<? extends T1> o1, Observable<? extends T2> o2, Observable<? extends T3> o3, Observable<? extends T4> o4, Func4<? super T1, ? super T2, ? super T3, ? super T4, Observable<? extends R>> zipFunction) {
        return Observable.merge(Observable.zip(o1, o2, o3, o4, zipFunction));
    }
}

回答2:

What about this:

public static <A,B,C> Observable<C> flatZip(Observable<A> o1, Observable<B> o2, F2<A,B,Observable<C>> transformer) {
    Observable<Observable<C>> obob = Observable.zip(o1, o2, (a, b) -> {
        return transformer.f(a, b);


    });

    Observable<C> ob = obob.flatMap(x -> x);

    return ob;
}

Of course, you'll need one for each number of arguments, but that's how it goes with zip, too. Guessing that is not the pain point here.

回答3:

Here is what I've ended up using in my project:

/**
 * Zips results of two observables into the other observable.
 * Works like zip operator, except zip function must return an Observable
 */
public static <T, V, R> Observable<R> flatZip(Observable<T> o1, Observable<V> o2, Func2<? super T, ? super V, Observable<R>> zipFunction) {
    return Observable.zip(o1, o2, Pair::new).flatMap(r -> zipFunction.call(r.first, r.second));
}

回答4:

Well the simplest thing to do would be as follows

final Observable<M> result = Observable.zip(obs1, obs2, (o1, o2) -> {
    return new M(o1, o2); // construct a new M and return it from here. 
});

Hope this helps

anand raman

来源：https://stackoverflow.com/questions/23721701/flatzip-in-rxjava