Is out there any Retrofit CallAdapter that returns...

# android

[Pablichjenkov]

Is out there any Retrofit CallAdapter that returns Flow<T>. Is it a bad design?

[jw]

Why do you want this over suspend fun?

[Pablichjenkov]

Just for symmetry with Rx. I am thinking on Rx1 migration to Flow.
I am most likely conceptually wrong trying to equate Observable and Flow.

[jw]

They are equivalent, but Observable is also somewhat incorrect for representing a network request. RxJava 2 fixed this with the Single type.

[Pablichjenkov]

for a network request thats right.. However, in other scenarios some of my streams emit more than one event, like State.Loading, State.Data.
What I normally do is having an Interactor/Actor chaining the Observables. I would like to do the same with Flow. suspend works is just that the chain does not look the same.
My knowledge on coroutines is entry level, there is probably a better way.

[jw]

Sure but Retrofit models only the network request part. You can convert Single to Observable where necessary and suspend fun integrates into Flow operators as well.

[Pablichjenkov]

and suspend fun integrates into Flow operators as well
Definitely a good approach, I haven’t tried. Thanks!

[gildor]

You even can easily convert suspend function to flow directly (like Single -> Observable), so it will be lazy, if you want:

::someFunction.asFlow()

[Pablichjenkov]

Thanks for replying.
You mean ::someSuspendFunction.asFlow right?

I still have a question either calling the retrofitApi.suspendingFunc() from an enclosing Flow or retrofitApi::suspendingFunc().asFlow().
If I want to propagate a custom CustomHttpException or CustomIOException down the stream. Should I enclose the retrofit api suspended call in a try/catch block, or append a .catch() operator after the Flow?
With Observables I use .onErrorReturn() operator to intercept erros.

[gildor]

You mean ::someSuspendFunction.asFlow right?

It works for suspend and common functions

[Pablichjenkov]

I just saw another scenario to convert to Flow, is when refactoring a zip operator. Is easier to wrap every retrofit api call in a Flow and keep the same code just replacing Observable.zip by Flow.zip than dealing with suspend functions+asyncBuilder+await+exception

[gildor]

retrofitApi.suspendFunc().asFlow() is incorrect, it should be retrofitApi::suspendFunc.asFlow() or suspend { retrofitApi.suspendFunc(param) }.asFlow()

[gildor]

If you just want to migrate existing Retrofit service with Observable, Flow is fine, but refactor code to use suspend functions for Network requests is much more clear and less error prone in most cases

[Pablichjenkov]

Oh ok, thanks for the clarification on .asFlow() usage. I just corrected my post so it does not confuse any reader.
I see the point, I will move into that direction then.

[gildor]

retrofitApi::suspendingFunc().asFlow() is still not correct, goal here is to convert method reference to flow, so when terminal operator will be called this method reference will be invoked by Flow chain