RxAndroid - Handle Errors with Zip operator - error-handling

Question

I'm trying to find a way to execute requests in parallel and handle them when every observable finishes. Despite everything is working when all observables gives a response, I not seeing a way to handle each all errors when everything is finished.
This is a sample of zip operator, which basically executes 2 requests in parallel:
Observable.zip(
getObservable1()
.onErrorResumeNext { errorThrowable: Throwable ->
Observable.error(ErrorEntity(Type.ONE, errorThrowable))
}.subscribeOn(Schedulers.io()),
getObservable2()
.onErrorResumeNext { errorThrowable: Throwable ->
Observable.error(ErrorEntity(Type.TWO, errorThrowable))
}.subscribeOn(Schedulers.io()),
BiFunction { value1: String, value2: String ->
return#BiFunction value1 + value2
})
//execute requests should be on io() thread
.subscribeOn(Schedulers.io())
//there are other tasks inside subscriber that need io() thread
.observeOn(AndroidSchedulers.mainThread())
.subscribe(
{ result ->
Snackbar.make(view, "Replace with your own action " + result, Snackbar.LENGTH_LONG)
.setAction("Action", null).show()
},
{ error ->
Log.d("TAG", "Error is : " + (error as ErrorEntity).error.message)
}
)
private fun getObservable1(): Observable<String> {
return Observable.defer {
throw Throwable("Error 1")
}
}
private fun getObservable2(): Observable<String> {
return Observable.defer {
throw Throwable("Error 2")
}
}
Problem with this approach is that there is no mechanism to join each error like BiFunction do for the success case. Therefore, the zip operator will only trigger the first error and will ignore the others.
Output:
D/TAG: Error is : Error 1
Is there any way to retrieve all errors only after every observable inside zip completed or gave an error?
My main goal is to see which requests gave an error and execute only those after a dialog appears to the user asking him if he wants to retry the failed requests.

Answer 1

You can model your observables using data classes. E.g.
sealed class Response {
data class Success(val data: String) : Response()
data class Error(val t: Throwable) : Response()
}
then you can map your observables to Response like this:
val first: Observable<Response> = observable1
.map<Response> { Response.Success(it) }
.onErrorReturn { Response.Error(it) }
val second: Observable<Response> = observable2
.map<Response> { Response.Success(it) }
.onErrorReturn { Response.Error(it) }
and you can combine them:
Observable.zip(
first,
second,
BiFunction { t1: Response, t2: Response -> Pair(t1, t2) }
).subscribe({println(it)})
this prints:
(Error(t=java.lang.Exception: Error 1), Error(t=java.lang.Exception:
Error 2))
Also take a look at this article.