what is the good way to writing this code: ```over...

# codereview

[Kashif]

what is the good way to writing this code:

override fun getOrderInfoList(status: String, chainID: String, debugTag: String): Flowable<Result<List<OrderInfo>>> {
    logger.d(TAG, "Getting order list for status %s", status)
    val fetchFromStorageObservable = storageDataSource.getOrderList(debugTag)
    val observeStorageObservable = storageDataSource.observeOrderList(debugTag)
    // function which fetches from the local storage and takes a throwable that might be re-thrown if there's no data found locally
    val fetchFromStorageOrThrowObservable = fun (t : Throwable) : Observable<Result<List<OrderInfo>>> {
        fetchFromStorageObservable.map {
            if(it.isEmpty()) {
                // re-throw the exception from the Remote source since we got no data from the Local source
                throw t
            }
            it
        }
    }
    val fetchFromRemoteObservable = remoteDataSource.getOrderInfoList(status, chainID).toObservable().onErrorResumeNext { t: Throwable ->
        logger.d(TAG, "order list not received from server")
        // fallback to the local source
        fetchFromStorageOrThrowObservable(t)
    }.flatMap {
        if (it is Result.Success) {
            persisOrderInfoList(it.data)
        }
        fetchFromStorageObservable
    }
    return Observable.concat(fetchFromRemoteObservable, observeStorageObservable).toFlowable(BackpressureStrategy.LATEST)
}

[Kroppeb]

There are a lot of classes and classes where I don't have any information about

[Kroppeb]

Like what is the it in the fetchFromStorageObservable.map. Is it the list?

[Kroppeb]

And what type is fetchFromStorageObservable?

[Kroppeb]

Also the function for fetchFromStorageOrThrowObservable doesn't have a return statement?

[Kroppeb]

Also Result.Success doesn't exist. Is this a self-defined type?

[Kashif]

“what is the it in the fetchFromStorageObservable.map. Is it the list? ”
yes it is List<OrderInfo>

“what type is `fetchFromStorageObservable`”?
Observable

“Also the function for fetchFromStorageOrThrowObservable doesn’t have a return statement”?
true, my bad, forgot to add return statement

"Result.Success doesn’t exist. Is this a self-defined type”?
yes it is self-defined type which is like:

sealed class Result<out T : Any> {

    data class Success<out T : Any>(val data: T) : Result<T>()
    data class Error(val exception: Exception) : Result<Nothing>()

    override fun toString(): String {
        return when (this) {
            is Success<*> -> "Success[data=$data]"
            is Error -> "Error[exception=$exception]"
        }
    }
}

[Matteo Mirk]

Why not use Kotlin’s Result?
https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-result/index.html

[Kroppeb]

Because getOrderInfoList returns a Result I think, which is not possible with a Kotlin Result.

[Kroppeb]

It seems I made all the right guesses. Though does this mean that map is an extension-function defined on Observable<Result<T>>?

[Kashif]

yup true Robbe

[Kashif]

my point here is any other way to write better code than what i shared?