Is there something I can do for the use case of I am observi

Question

Is there something I can do for the use case of I am observing a flow I want to start an infinite loop when I receive a specific type sealed limited options the flow gives me When I get the same type again I do not want to re start this infinite loop but let it keep going When I get a different type I want to stop that old infinite loop and do nothing until I again get the type I m looking for Code ```sealed interface Types object One Types object Two Types val someFlow Flow lt Types gt someFlow filterIsInstance lt Types One gt distinctUntilChanged collectLatest one gt I want this to be cancelled on an emission of `Two` from `someFlow` but keep on going alive without interruption on a repeat emission of `One` if it was `One` before too coroutineScope while isActive doWork one ```

Stylianos Gakis · Answer

Hmm I am now doing ``` map it as Types One distinctUntilChanged collectLatest one Types One gt if one == null return collectLatest rest of loop code ``` And it seems to be working fine But the annoying part is that I need to manually exit it with the if check in the first line I guess this is unavoidable right And overall I just feel like this could be done a bit nicer without the null castings etc I would love to hear if someone has a better idea thinking face

expensivebelly · Answer

If I understand you correctly what you want is the equivalent in Flow of this Rx operator <https github com akarnokd RxJavaExtensions flowabletransformersvalve>

Stylianos Gakis · Answer

I ve never worked with RX honestly I m having a hard time understanding what the thing you linked to me does sweat smile RX looks like absolute magic to me tbh My use case is this I have a AudioPlayer class basically has a `MediaPlayer` inside of it but also keeps track of an internal State with the options `Playing Paused End` etc In order to then make sure my UI shows how far in the video we currently are since I don t think the Android `MediaPlayer` has a callback to report how far in the video it is I am this coroutine to every X milliseconds get the current progress ``` FloatRange from = 0 0 to = 1 0 private fun MediaPlayer getProgressPercentage Float return currentPosition toFloat duration toFloat coerceIn 0f 1f ``` to then in turn update the Playing state that also contains a progress Float inside of it And I want to start this coroutine when the state turns to `Playing` and let it report back really fast but then stop it when we re not on `Playing` anymore <https github com HedvigInsurance android blob bd355a953612dd9b71418fe67968d66196d05f3f app src main java com hedvig app feature claimdetail data AudioPlayer kt L79 L95|Here is the source code>

expensivebelly · Answer

```fun lt T Any gt Flow lt T gt valve valveSource Flow lt Boolean gt Flow lt T gt = this combine valveSource distinctUntilChanged value T valve Boolean gt value to valve mapNotNull value valve gt value takeIf valve ```

Stylianos Gakis · Answer

I am actually quite confused as to how this would be applied to solve my problem thinking face

expensivebelly · Answer

```someFlow distinctUntilChanged flatMapLatest types gt if types is Types One flow while true emit doWork types else emptyFlow ```

expensivebelly · Answer

You re right `valve` does not apply to your specific problem but the code snippet above it should

Stylianos Gakis · Answer

What I did settle with is this and it s working good enough ```audioPlayerState map type gt type shouldContinuouslyDoWork added this as a property to Types to make this easier distinctUntilChanged collectLatest shouldContinuouslyDoWork Boolean gt if shouldContinuouslyUpdateProgress coroutineScope while isActive delay doWork else doWork ``` Since I am doing the work in line there and don t need to transform this to another flow to be used somewhere there was no need for the flatMapLatest that you suggested But if I did that looks like a great approach yeah Thanks a lot for trying to help me out btw

expensivebelly · Answer

Yeah the idea is the same normally I expose Flows in ViewModel and collect them in the View I find it easier to test that way using Turbine I would be keen to see how you re testing that code if you don t mind Thanks

Stylianos Gakis · Answer

This is in a bit of a different context not a ViewModel exposing flows and a view observing them It s a class that does all the work inside itself and exposes a simple that exposes three functions to start stop seek on the media player and a StateFlow with it s current internal state for the UI to observe Implementation is With that said I am not testing this oops flushed so yeah