How would you people improve this code? ```suspend...

# arrow

[jean]

How would you people improve this code?

suspend fun <T> getListWrapperFromDbAnApi(
    getFromDb: suspend () -> Either<InOrderError, ListWrapper<T>>,
    shouldUpdate: (List<T>) -> Boolean,
    getFromApi: suspend () -> Either<InOrderError, ListWrapper<T>>,
    saveDataFromApi: suspend (List<T>) -> Either<InOrderError, Unit>
) = flow {
        getFromDb().fold(
            { emit(Either.Left(it)) },
            { dbData ->
                emit(Either.Right(dbData))
                if (shouldUpdate(dbData.items)) {
                    getFromApi().fold(
                        { emit(Either.Left(it)) },
                        { apiData ->
                            if (dbData != apiData) {
                                emit(Either.Right(apiData))
                                saveDataFromApi(apiData.items)
                            }
                        }
                    )
                }
            }
        )
    }

I don’t think I can use either.eager due to the nested suspend function error Restricted suspending functions can only invoke member or extension suspending functions on their restricted coroutine scope

[simon.vergauwen]

But you can use either { } inside flow { } since it’s suspend, right?
So something like this.

flow {
  either<InOrderError, Unit> {
    val dbData = getFromDb().bind()
    emit(dbData)
    if(shouldUpdate(db.item)) {
      val apiData = getFromApi().bind()
      if(dbData != apiData ) {
        emit(apiData.right())
        saveDataFromApi(apiData.items)
      }
    }
  }.fold({ emit(it.left()) }, ::identity)
}

[jean]

TIL about either , thanks @simon.vergauwen!

[jean]

.fold({ emit(it.left()) }, ::identity) is also pretty neat

[jean]

not so nice after all, I had to do this in order to make it work properly

flow {
    val collector = this
    either<InOrderError, Unit> {
        val dbData = getFromDb().bind()
        collector.emit(Either.Right(dbData))
        if (shouldUpdate(dbData.items)) {
            val apiData = getFromApi().bind()
            if (dbData != apiData) {
                collector.emit(Either.Right(apiData))
                saveDataFromApi(apiData.items)
            }
        }
    }.fold({ emit(it.left()) }, ::identity)
}

emit isn’t directly accessible inside either since lambdas have different scope

[simon.vergauwen]

That is very strange… I’ll try this example

[simon.vergauwen]

either is even inline

[simon.vergauwen]

Works fine for me

[pakoito]

.fold({ emit(it.left()) }, ::identity)

mapLeft here

[jean]

This little guy break the whole thing emit(dbData) , using emit(dbData.right()) instead fixed the issue