I was thinking about the rx java coroutine await

Question

< elizarov> I was thinking about the rx java coroutine await I think it might make sense to create a wrapping class that encapsulates the error sucess

elizarov · Answer

This result class is called `Try` in Scala because of try monad I cannot convince myself that it is useful enough to include it and it is very easy to write if you need it I will appreciate if you or < gildor> share some real life use cases for such a class

Paul Woitaschek · Answer

Well RxJava s onError quite common because composing is so easy But when writing iterative code error throwing stuff is pain

Paul Woitaschek · Answer

```kotlin async try val user = userManager user await try val movies = movieManager getMoviesForAge user age val firstMovie = movies first catch e IoException showNetworkError catch e show catch e IoException showNetworkError catch e HttpException if e code==400 showNotSignedInException else showNetworkError ```

Paul Woitaschek · Answer

Stuff like that

elizarov · Answer

You can write one try at the outermost level Preferably in some kind of framework your own wrapper for async for example I don t see any value in those nested trys

Paul Woitaschek · Answer

Depending on where the exception happens they mean different things

elizarov · Answer

I d be really grateful for a chance to look at that in a larger context a part of some real app Do you know of any open source apps with this kind of logic

gildor · Answer

< elizarov> This approach is mostly experimental for me I m trying to understand what is the most convenient way to use it I had 3 main goals with Result sealed class monad 1 3 types of answer HTTP success HTTP error and other exceptions Because Retrofit Call has such separation but HTTP success and error has the same additional wrapper 2 Easy to write extension functions for such class then implement a lot of coroutine implementations I have getOrNull getOrThrow and getOrDefault For some real cases in UI it s just allow to write less code because sometimes you don t care if http or network error happened and you don t want to handle exception especially inside loops 3 `when` block especially with 3 cases looks better then `try` with two `catch` blocks Actually I m not evangelist of this approach I m still not sure what will be more useful in the real app and how good this practice And it s the reason why I ve implement ` await ` that throws exception and ` awaitResult ` with Result class I m writing Android sample app that uses coroutines for different async operations to show some examples of usage coroutines in Android and understand for myself how to better use it

elizarov · Answer

Thanks for detailed explanation It would be interesting to hear your experience with the sample app