Shortcut for a combine resulting in another uni

[lordvlad]

Description

I often need to combine a list of Unis's outcomes to another Uni.
Right now I have two options to do so:

| EDIT: uniA and uniB are of different Types

Uni<A> uniA = getUniA();
Uni<B> uniB = getUniB();

// Option A
Uni.combine().all().unis(uniA, uniB).combinedWith((a, b) -> makeNewUni(a, b)).flatMap(identity())

or

// Option B
Uni.combine().all().unis(uniA, uniB).asTuple().flatMap(tuple -> makeNewUni(tuple.getItem1(), tuple.getItem2())

both of which are not too pretty.

I guess an overloaded combinedWith which accepts a FunctionX<..., Uni<R>> would do the trick. A simple sugar for Option A. I wouldn't mind if it would be called combinedWithUni or something similar.

[jponge]

How about Uni.join()? (note that a PR to fix generics here is coming today)

[lordvlad]

I was under the impression that Uni.join() was intended for use on uniform lists of unis (i.e. List<Uni<T>>). I like combinedWith because it allows for unequal Unis to be handled by an combiner, and depending on the number of unis, i can choose from a number of combiners.

[jponge]

There's a good chance you might want to transform values from different sources to be joined, and have homogenous types at the join level.

[lordvlad]

Right. for that case it is settled then, just use Uni.join(). But for the case of disparate types that need to be combined, can we have a shortcut/sugar for Option A?

[jponge]

Something like combineToUni?

[lordvlad]

At which position?
Uni.combineWithUni().all().unis(...).combined with(...) or Uni.combine().all().unis().combinedWithUni?

[jponge]

Something like Uni.combine().all().unis().combinedWithUni()

[acasanova99]

Yes, it would be a good enhancement. For instance:

Current code:

return Uni.combine().all().unis(a, b)
        .combinedWith((aa, bb) -> {
        ...
        ...
        }).flatMap(identity()); // .flatMap(x->x) in order to remove one Uni warping

Proposed code:

return Uni.combine().all().unis(a, b)
        .combinedWithUni((aa, bb) -> {
        ...
        ...
         });

[lordvlad]

Feature request and PR found here #919