amb (race) as a new FlattenStrategy

[inamiy]

Just got inspired from ReactiveCocoa/ReactiveObjC#51, I think we can add FlattenStrategy.first where multiple producers race and winner forwards all the events after they get flattened.

Diagram: http://reactivex.io/documentation/operators/amb.html

I think this can be useful in some scenario (though I have never used it before).

[NachoSoto]

Wouldn't that be equivalent to

nestedSignal
  .take(1)
  .flatten(.Merge) // or anything else

[mdiep]

No, I think it's the first flattened signal to send an event.

let (s1, o1) = Signal.pipe()
let (s2 o2) = Signal.pipe()
let (s3, o3) = Signal.pipe()

Signal(values: s1, s2, s3)
    .flatten(.first)
   .observeValues { print($0) }

o3.send(value: 7) // s3 becomes the chosen signal and its values are used

It makes sense to me as a possible strategy, but I'm not sure what you'd use it for.

[inamiy]

One example would be func timeout that can be re-implemented like this:

public func timeout(after interval: TimeInterval, raising error: Error, on scheduler: DateSchedulerProtocol) -> SignalProducer<Value, Error> {
    return SignalProducer(values: [
        self, 
        SignalProducer(error: error).delayError(interval, on: scheduler)
    ]).flatten(.first)
}
// NOTE: `delayError` doesn't exist yet

[RuiAAPeres]

@inamiy any progress on this? 😊

[inamiy]

@RuiAAPeres Not yet, but I will tackle on this soon :)

[andersio]

Implemented in #233.