i am migrating from rxjava to coroutines and just stumped on something now. is there an equivalent t...

# android

[lawlorslaw]

i am migrating from rxjava to coroutines and just stumped on something now. is there an equivalent to

local.onErrorResumeNext { remote }

with coroutines?

[gildor]

local.catch { emitAll(remote) }

[gildor]

Also you can see that onErrorResumeNext exists for Flow, but it’s deprecated and provides replacement it made this way to help users who more familiar with rxjava to find Flow operators

[lawlorslaw]

i am trying to rewrite this rxjava code

Untitled.kt

[lawlorslaw]

so far this is what i have but i know its incomplete

Untitled.kt

[gildor]

catch { flowOf(remote) }

You need catch { emit(remote) }

[gildor]

What is type of coinLocalDataSource.getCoins().? If it Flow, why you do flowOf(local)

[gildor]

Also what is type of coinRemoteDataSource.getCoins()? Is it just suspend function? If so, you need:

.catch { emit(coinRemoteDataSource.getCoins()) }

[gildor]

It’s not good style to have suspend function which returns Flow, I believe you need it only because of getCoins, so you can just move it to catch and it will allow make function not suspend

[lawlorslaw]

yeah i am not very familiar with Flow, so that may just be a misuse

[lawlorslaw]

this is coinLocalDataSource.getCoins()

suspend fun getCoins(): List<CoinEntity> {
        return coinDao.getAllCoins()
    }

[lawlorslaw]

this is coinRemoteDataSource.getCoins()

suspend fun getCoins() : List<CoinResponse> {
        return coinService.getCoins()
    }

[lawlorslaw]

btw thank you so much for all of your help

[gildor]

if both of those functions are just suspend, why you even need Flow?

[lawlorslaw]

i don’t think i need Flow

[gildor]

why not rewrite it as simple suspend function:

[lawlorslaw]

yeah i would prefer to keep it simple

[gildor]

yep, looks that you just need suspend function

suspend fun getCoins(): List<CoinResponse> {
        
          val local = coinLocalDataSource.getCoins()
          return if (local.isEmpty()) {
             coinRemoteDataSource.getCoins()
          } else {
             local
          }.map { it.toResponseModel() }
}

[gildor]

Only don’t forget that getCoins will not catch exceptions

[lawlorslaw]

okay that almost has everything

[lawlorslaw]

but what about this piece …

val remote =
      coinRemoteDataSource.getCoins()
.doOnSuccess {  
   coinLocalDataSource.saveCoins(it.toEntityModels())
}

[gildor]

val local = coinLocalDataSource.getCoins()
          return if (local.isEmpty()) {
             val remote = coinRemoteDataSource.getCoins()
             coinLocalDataSource.saveCoins(remote.toEntityModels())
             remote
          } else {
             local
          }.map { it.toResponseModel() }

[gildor]

Really, like any other non-reactive code

[lawlorslaw]

i think this is what i need

suspend fun getCoins(): List<CoinResponse> {
        val local = coinLocalDataSource.getCoins()
        return if (local.isEmpty()) {
            val remote = coinRemoteDataSource.getCoins()
            if(remote.isNotEmpty())
                coinLocalDataSource.saveCoins(remote.toEntityModels())
            remote
        } else {
            local.toResponseModels()
        }
    }

[gildor]

yep