whenAll: always yields [RACUnit defaultUnit]

[bvanderveen]

The implementation of whenAll::

+ (RACSubscribable *)whenAll:(NSArray *)subscribables {
    return [self combineLatest:subscribables reduce:^(RACTuple *xs) { return [RACUnit defaultUnit]; }];
}

The call to sendNext: within combineLatest:reduce:

[subscriber sendNext:reduceBlock([RACTuple tupleWithObjectsFromArray:orderedValues])];

The result is that subscribers to the subscribable returned by whenAll: always receive [RACUnit defaultUnit]. Unless I'm missing something obvious.

A possible fix would be:

+ (RACSubscribable *)whenAll:(NSArray *)subscribables {
    return [self combineLatest:subscribables reduce:^(RACTuple *xs) { return xs; }];
}

Thoughts?

[jspahrsummers]

This is what the method is documented to do. Are you saying that you would prefer a different interface? If so, what would be the motivation?

[bvanderveen]

Currently, the subscribables passed to whenAll: have to side-effects to capture their values (if any). It would be nice if the value yielded by whenAll: was an ordered tuple of the values of the subscribables from which it was created, rather than a unit value.

[bvanderveen]

Ah yes, missed that documentation. :S

I would prefer the return value be a tuple so I don't have to introduce side-effects (e.g., doNext:) to retrieve those values. I could achieve the same result with combineLatest:reduce: (where the reduceBlock is a simple identity, as in the change I proposed) but it might be nice to have a shorthand for that.

[bvanderveen]

Compare .NET ForkJoin: http://msdn.microsoft.com/en-us/library/ff708019(v=vs.92).aspx

[joshaber]

-whenAll: in its current form is pretty minimally useful. The name also seems odd to me. Feels more like -whenAny: than -whenAll:. Lol @ Pastjosh. So what if we do this. Deprecate -whenAll:, add -whenAny: which passes the tuple from combineLatest:reduce: through.

[jspahrsummers]

I'm 👍 on making the changes discussed in this thread. I think it makes the most sense to just add a combineLatest: (with no reduce block) method, though. That gives you API consistency, and has a more transformative (rather than effective) feel.

[joshaber]

@jspahrsummers I almost suggested that but it felt weird to call it -combineLatest: when it wasn't actually, you know, combining (well, I guess it does into a tuple but whatev).

[jspahrsummers]

Right, it combines into a tuple. I don't know why that's any less of a combination. :P

[bvanderveen]

👍 for adding -combineLatest: which has the same behavior as -whenAll: except that the tuple of values is returned.

[bvanderveen]

Perhaps +combineLatest:reduce: could be deprecated in favor of composing +combineLatest: with a -select:?

[jspahrsummers]

Fixed by #44.