kotlinlang #rx

Have you ever been confused on what the flatmap and map operators are? Hopefully this post is of help https://twitter.com/RakeebJH11/status/963423436298125312

damian

02/23/2018, 2:05 PM

question on combining streams: i have a state observable which can emit random states. the first emission can take up to 10-15 seconds. also, i want to display a countdown for one of the state’s properties (

timeLeft

in seconds). my first approach was

combineLatest(state, Observable.interval(1, TimeUnit.SECONDS))

but the timer seems to start before i even receive a state, thus my countdown is wrong. my next approach would be

state.switchMap { state -> Observable.interval(1, TimeUnit.SECONDS). map { elapsedTime -> state.timeLeft - elapsedTime}}

- is there a “better” approach to this?

kluck

02/23/2018, 2:48 PM

Hello guys, I'm looking for a way to kind of combine throttleFirst and distinctUntilChanged: if I have 2 distinct elements, no matter the delay between the emissions, I want to receive both. But if I get the same element multiple times, I want it to be throttled and get one, say every 2s. Any idea how I could manage that?

rudolf.hladik

02/26/2018, 8:38 AM

hi, is there a nice way to lazy initialize property from onSuccess/onNext of Single/Flowable ?

lexardi

03/05/2018, 11:07 AM

Hi there, as doc says, disposable is not usually disposed by itself, so I need to dispose it manually in android lifecycle (in my case). Therefore I have necessity to make disposable global variable and put

if (disposable != null) dispose()

in every onDestroy(). How to facilitate this process?

edwardwongtl

03/05/2018, 11:11 AM

You can also hide this boiler plate in the base class of your activity, and use a

compositeDisposable

to hold all

disposable

in a single place.

ubu

03/07/2018, 6:02 PM

Hello everyone. I have two buttons which can be clicked at the same time. I would like to get notified on the event of the button that was clicked first in this case, the second event must be ignored. What operator should I use in this case? I use RxBinding events.

locke

03/13/2018, 2:21 PM

@gildor Are you sure you can't

map

the

BehaviorSubject

? Not trying to argue, but the above does allow values to be pushed into it? I'm not quite sure what you mean by the alternative solution. The general goal is to have this

Subject

observer listen to values of this

List

, and emit

filtered

versions of the

List

. New to Rx, so maybe I have the structure of the way this should work setup incorrectly. It was my understanding that

Subjects

act as both

Observer

and

Observable

adams2

03/14/2018, 11:08 PM

do ya'll inject your rxjava schedulers

03/20/2018, 8:11 PM

upstream.publish { zip(it, it.skip(1), it.skip(2), ::Tuple) }

edwardwongtl

03/21/2018, 5:35 AM

getItems().first(default).map{ it.isNotEmpty() }

should do the trick

gildor

04/05/2018, 11:31 AM

Could you show an example? In general blockingFirst sounds bad and flatmap is standard way to do that

04/06/2018, 2:17 AM

you want something like

return parents.flatMapIterable { it }
    .concatMap { parent -> Single.zip(getFirst(parent), getSecond(parent), { first, second -> parent.copy(first = first, second = second) }) }
    .toList()

🙂 1

04/06/2018, 2:18 AM

the lack of polymorphic types in RxJava is such a bummer

☝️ 1

vander2675

04/09/2018, 7:56 AM

I love the syntax, these Extension give me so I tried modeling my Database with Extension Functions like:

ubu

04/09/2018, 12:02 PM

Hi everyone. Having the following flow of events (there’s a button click that toggles some state):

state1 -> state2 -> state1 -> state2 -> state1 -> state2 -> ...

When there’s no event within 3 seconds, restore default state (state1). How would I do that? Any help would be appreciated.

ursus

04/14/2018, 3:40 AM

is there a way around

BiFunction { user: User, token: String -> Tuple2(user, token) }

in rx with kotlin?

ursus

04/14/2018, 3:55 AM

is there a sort of a "sideffect flatmap"? i.e. like doOnNext but with observable, where I want to execute it but want to still keep upstream returned value

ubu

04/17/2018, 6:44 PM

Hi there. When I have a lot of Observables (

RxView.clicks(someButton)

), what would be the best way to unsubscribe/disable all other buttons when ButtonX is pressed?

ursus

04/18/2018, 3:14 AM

Hi, is there a way for a custom observable created via Observable.create() to emit on scheduler specified via subscribeOn if wrapped async api changes thread of callback? (Other than observseOn...) I.e. I have bluetooth android API I am wrapping, and it automatically emits its callbacks on main thread, and id like to keep the subscribeOn scheduler

GurpreetSK

04/18/2018, 6:29 PM

Hey! Needed some help. Is there a way I can get a value out of a

single

if it is empty? For example, I have my DB call returning a single and want to return a boolean value on basis of whether it is empty or not. I'm doing the following currently, but it doesn't seem to work as the control gets blocked (as the table is empty).

myDao
    .getAll(object.id())
    .isEmpty
    .blockingGet()
    .not()

ursus

04/18/2018, 7:48 PM

@GurpreetSK if value not being there is valid state, then expose it as optional ...Single<Optional<T>>

👍 1

dknapp

04/18/2018, 8:58 PM

couldn’t you use a Maybe for that

edwardwongtl

04/20/2018, 3:41 AM

onErrorResumeNext { t: Throwable -> ... }

04/20/2018, 7:58 PM

you almost never want to use a subject as an observer in the sense that you subscribe it to another stream

👍 1

Paul Woitaschek

04/23/2018, 9:47 AM

That's really not a managable way of handling rx. That puts ton of state all over the place. Just call

executeRequest

a couple of times and you're into the fun 🙂

☝️ 1

04/27/2018, 5:31 PM

.publish().refCount()

👍 2

blakelee

04/27/2018, 11:17 PM

I used share and made it a variable so that multiple subscribers can subscribe one observable and only fire the event when there observers. However, I have a repeatWhen that fires off after a few seconds and the id is not getting updated even if I change it

private var id = 1
private val getItem: Observable<Any> =
    service.getItem(id) // a Single
        .toObservable()
        .repeatWhen { completed -> completed.delay(3, TimeUnit.SECONDS) }
        .share()

Slackbot

05/02/2018, 6:38 AM

This message was deleted.

ursus

05/03/2018, 1:09 PM

guys, in rxjava2 observable when backpressured