staltz/xstream

An extremely intuitive, small, and fast functional reactive stream library for JavaScript

adz5a

@adz5a

as the memory stream will emit its last emitted value, you could stream.take(1).addListener to retrieve the stored value

jfcha

@jfcha

I was hoping to avoid going through a listener, but good to know that'll work. Thanks. I suppose getting values outside of the stream isn't really ideal behavior so having to pay a tax on it makes some sense.

adz5a

@adz5a

i don't think there is another way to "unwrap" values from a stream apart from a listener, what is your use case, maybe i can help :)

jfcha

@jfcha

It's a bit complicated and I have a work around. I was just hoping for a lazy answer :) . Thanks for the offer though! If I come up with a succinct case I'll ask again.

adz5a

@adz5a

hello, I have a case

a problem, that i don't quite understand, I made gist of it

https://gist.github.com/adz5a/1f28dacbf6e2c9a97c8466b9c179e2ea

i'm trying to understand why my get function is getting increasedly more called

it's not a bug I guess ( i made a similar gist with most.js and I have the same behaviour ) : I receive only "1--lol--lol" the expected number of times, but my get function is being called a lot : once the first time, two times the second and so on...

André Staltz

@staltz

Hi @adz5a. There are 3 nested flattens, that looks very weird

I suspect, depending on what you want to achieve, you can simplify this a lot

adz5a

@adz5a

Probably, the idea is this :

i have a stream with a low frequency : props$. When it emits I generate a second stream which models input from the user, and at each new value from the second one, i make an asynchronous operation and merge back the results

( I am using the componentFromStream operator from recompose )

I will try and simplify it, I think I don't understand fully what i am trying to achieve here...

Jules Sam. Randolph

@jsamr

Hi ! Really enjoying reactive programming thanks to cycle + xtream. I can't find the zip operator ; has anyone written a custom extra ?

Michal Vanko

@michalvankodev

@sveinburne Perhaps you are looking for https://github.com/staltz/xstream/blob/master/EXTRA_DOCS.md#concat

Jules Sam. Randolph

@jsamr

@michalvankodev thanks, but unfortunately it's different, see those marbles : http://rxmarbles.com/#zip http://rxmarbles.com/#concat

Churchill Lee

@FeliciousX

@sveinburne u might want to read up on this https://staltz.com/rx-glitches-arent-actually-a-problem.html

Jules Sam. Randolph

@jsamr

@FeliciousX Oh thanks of lot, now I understand I might have had a design issue in the first place ! Will go for sampleCombine now.

Churchill Lee

@FeliciousX

Max Battcher

@WorldMaker

I've got a map(...fromArray(Stream<any>[])).flatten().compose(flattenConcurrently) and I remove a Stream from the array but its handlers never get removed and it's dispose()/cancel() is never called.

Is there some better way I'm missing for such a dynamic set of streams with xstream?

Or did I discover some edge case bug? I don't recall having an issue like this with Rx, but this particular code is brand new so I don't have a direct Rx equivalent to compare so I could be forgetful.

Max Battcher

@WorldMaker

Worse, the final Listeners down the line seem to somehow get rebound every time the top level Stream[] changes, so start to see duplicate notifications, etc.

The answer could also be my brain is mush today and I'm missing something obvious.

Max Battcher

@WorldMaker

Ah, yeah: It's probably that I want map(...fromArray().compose(flattenConcurrently)).flatten(), instead, isn't it? Another case where writing the problem down makes it more obvious.

Max Battcher

@WorldMaker

Huh, but now I need to prune already completed ones to keep them from resubscribing... Fun.

Max Battcher

@WorldMaker

Ah yes, I already have an out-of-band signal to help with that. Thanks for listening mostly inactive room.

André Staltz

@staltz

Thomas Grainger

@graingert

is there a .debug that's just for errors?

@staltz ^

André Staltz

@staltz

I think you'd have to use replaceError @graingert

Thomas Grainger

@graingert

@staltz yeah I did that and it was way better. I can put the error message in the virtual Dom

And a progress indicator for submitting to sentry!

Michal Vanko

@michalvankodev

Is it wanted behaviour for xs.combine to not emit anything when you only combine one stream? eg. xs.combine(match$).map....

Not crucial.. just wasn't expecting it to not work

Nick Johnstone

@Widdershin

@michalvankodev seems to be working for me:

 λ node                                                    
> const xs = require('xstream').default
>  xs.combine(xs.of('hi')).addListener({next: console.log})
[ 'hi' ]

(tested against the latest version of xstream)

Perhaps there's something else going on

Maybe the stream is never being subscribed to

λ • Geovani de Souza

@geovanisouza92

I have this use case, but I'm not totally sure how to achieve this: the source observable/stream will produce events sequentially, then I want to queue those events on a limited count (similar to what bufferCount does), but instead emitting arrays with those events, I want to "resolve" (think on Promise) each event and emit the result (similar to map+flatten), and this "queue operator" queue the source events, then, when one event resolves, it pick another event from the queue and continue, it will not wait for the given count to be emitted from the source, but will limit concurrent events to that count. Am I making sense? Well, I would like something similar to https://www.npmjs.com/package/throat, but for Observable/Stream. I'm thinking on a custom operator, but do you have another idea?

λ • Geovani de Souza

@geovanisouza92

well, it seems that the past @staltz already answered me :joy: https://stackoverflow.com/a/26126750/3415659

André Staltz

@staltz

Sudarsan Balaji

@artfuldev

I wanna create a diff stream with time between its events. How do I do that?

const source$ = xs.fromArray([[1,2],[1],[1,2,3,4,5]]);
const required$ =
  source$
    .startWith([])
    . // what should I do here, to get
      // -[]--[1]--[1,2]--[1]--[1,2]--[1,2,3]--[1,2,3,4]--[1,2,3,4,5]-|

The -- is constant time between the diff events

trying to modify a list of items slowly (one-by-one) even though I get all of them at a time

Michael Maier

@maiermic

how can I duplicate the first element of a stream?

Michael Maier

@maiermic

well it seems I have another issue
at least Stream.merge(elements$, elements$.take(1)) is working

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