Question: How to concatenate streams that terminate? about reactkit

[DarthMike]

I've come up with a solution that makes it work. But I'm not sure it's elegant or correct. Some part of the code:

let stream = api.search(barcode)
                |> map { $0.searchableName }
                |> concat(Stream.never()) // Between stream boundaries
                |> flatMap { name in
                    return bgg.searchGames(name, type: .Games, match: .Loose)
                } |> take(1)

So basically I insert a never stream between stream boundaries, to keep the next stream alive.

[inamiy]

Thanks for pointing out this issue.
Current flatMap() has a different implementation compared to other Rx frameworks,
and I should say this is a bug.
Your code will be a good workaround, and I will try fixing this issue soon.

[DarthMike]

Thanks @inamiy .
I've got another question regarding streams which are bound. What is the behaviour of error propagation?

let stream = api.search(barcode) 
                |> flatMap {
                    return anotherStream(...)  // This stream fails via reject()
                }

I have two streams concatenated via flatmap, and then the second is rejected, but stream failure or completion callback is not called. Any clues what I might be missing?

[inamiy]

@DarthMike
In your case, if anotherStream(...) gets rejected, stream will also get rejected.
You can register callbacks likestream.failure(callback) or stream.then(callback) to check its being called, but doesn't it work for you?

[DarthMike]

@inamiy I subscribe via:
stream.react {
...
}.failure {
...
}
But don't receive callbacks for failure

[DarthMike]

@inamiy Let me elaborate: It may be a side effect of my workaround with Stream.never().
The actual stream composition is:

 let stream = api.search(barcode)
                |> map { $0.searchableName }
                |> concat(Stream.never())
                |> flatMap { name in
                    return anotherStream(...)
                }

I've tried pointing my code to the FlattenStyle branch, and refactoring it to look like:

 let stream = api.search(barcode)
                |> map { $0.searchableName }
                |> flatMap(.Concat) { name in
                    return anotherStream(...)
                }

Then works properly with react + failure.

[inamiy]

@DarthMike
Hm, actually, I don't think concat(Stream.never()) in your first code will affect the error propagation to downstream, so it should work just similar to second code...

But anyway!
Important part is your second code, and if that's working correctly,
I think we are now able to merge #44.

Thanks for checking this issue 😊