How to return an Observable from a Completable I ve tried th

Question

How to return an Observable from a Completable I ve tried this but I couldn t get mObservableData on subscription ```return data flatMapCompletable andThen mObservableData ```

gildor · Answer

What do you mean How to return an Observable from a Completable

gildor · Answer

Something like that ` andThen someLazyObservable `

memphis · Answer

I mean after not from sorry

gildor · Answer

`andThen` has different overloaded versions including one for Observable eager and lazy

memphis · Answer

I mean this one `andThen Observable `

gildor · Answer

What is your problem with this

gildor · Answer

andThen allows to chain completable with any other RxJava primitive what exactly doesn t work

arekolek · Answer

``` Observable just 1 2 3 flatMapCompletable Completable complete andThen Observable just 3 4 6 test assertValues 3 4 6 ``` worked for me

gildor · Answer

of course It should work never see problem with `andThen`

memphis · Answer

```fun getUsers Observable lt User gt return getUserInfo map flatMapCompletable it saveToRealm andThen usersFromRealm ```

memphis · Answer

I receive data from API so I want to save it to db first then return an Observable `usersFromRealm `

arekolek · Answer

what type is `saveToRealm `

memphis · Answer

It s a Completable

arekolek · Answer

are you sure `getUserInfo` emitted anything

memphis · Answer

Yes data are saved in db

arekolek · Answer

does `saveToRealm` signal `onSuccess` when that happens slightly smiling face

arekolek · Answer

two things I d try 1 replace `it saveToRealm ` with `Completable complete ` 2 replace `usersFromRealm ` with `Observable just User `

memphis · Answer

yes it signals `onComplete`

memphis · Answer

`saveToRealm ` ```return userInfoObservable flatMapCompletable Completable fromCallable it save ```

arekolek · Answer

I mean in the implementation of `getUsers` I d change that just to check if it s correct

memphis · Answer

Actually I ve tried the second one `Observable just User ` and got nothing

arekolek · Answer

maybe try 1 and 2 at the same time

arekolek · Answer

that should work without any issue I suppose

memphis · Answer

I did try both now nothing in return

memphis · Answer

There are no issues with the ViewModel

arekolek · Answer

how do you subscribe to it

arekolek · Answer

what if you create a unit test and invoke `getUsers test assertValue User ` with 1 and 2

memphis · Answer

```mGetUsersUseCase execute doOnNext mUserLiveData value = it doOnCompleteLog autoDisposable this subscribeWith RxLogSubscriber UserViewModel class java simpleName ```

memphis · Answer

`doOnCompleteLog` is just an extension

memphis · Answer

Ok I ll do it

arekolek · Answer

BTW isn t `LiveDataReactiveStreams fromPublisher` the same as what you are trying to achieve here with `liveData value = it` and `autoDisposable`

gildor · Answer

btw why do you request the same data from realm Maybe just do something like `userInfoObservable flatMap it apply save ` I just not sure how realm works maybe there is no data in databaase yet or some cache or any other issue Probably you could reproduce your problem on some self contained sample

memphis · Answer

I tried `getUsers test assertValue User ` and got an NPE

memphis · Answer

`LiveDataReactiveStreams fromPublisher` is a good practice Because I heard it s not

arekolek · Answer

about npe you probably need to mock `getUserInfo` to return some observable but that s a guess

arekolek · Answer

about `fromPublisher` I d be interested to hear about any problems with it but I don t know about any

memphis · Answer

< gildor> I want to return a `Completable` that s why I m using `flatMapCompletable`

gildor · Answer

But you return observable with data after completable that s my point you save something to do and then request it immediately

memphis · Answer

`it save ` doesn t return an observable

memphis · Answer

Actually that s what I wanted To save data to Realm from API and return an observable from the database that s why I do request it immediately Is there another option

gildor · Answer

Check my code snippet It returns it and calls save as side effect

gildor · Answer

Another option save but do not request data from db again but just return it

memphis · Answer

So I understand that data returned will be from the API not from Realm Is that what you re saying

gildor · Answer

I suppose you problem is that observable from db do not return to you just inserted data for some reason

gildor · Answer

Yes

gildor · Answer

At least for this particular case when save to db is just side effect

memphis · Answer

I was doing this before

memphis · Answer

So I can t just listen on the db with an Observable and once data are saved I get it

gildor · Answer

I don t know how Realm and Realm Rx API works but I can imagine API when you return observable that emits only new items updates of items But return data immediately rather than request it from db looks as more efficient and fast way

memphis · Answer

Thank you guys for help slightly smiling face < gildor> < arekolek>

Davor Maric · Answer

Sorry for bumping but I had simillar problem few days ago You can chain multiple calls with zip

gildor · Answer

Zip can be used to chain request but just for chaining there are more suitable operators most common of them is flatMap and andThen for Completable

gildor · Answer

Also zip is not available on Completable

Davor Maric · Answer

Well you can go with Single zip and then flatMapCompletable

Davor Maric · Answer

andThen requires another dependency

Davor Maric · Answer

I tend to avoid that as I m not really sure about reuseability to other RxExtensions

gildor · Answer

It s not true andThen is not another dependency this is standard method of Completable in RxJava1 and RxJava2

gildor · Answer

Could you please provide an example of Single zip for chaining I really not sure that this is the best solution for pure chaining but maybe you could show me a good use case

Davor Maric · Answer

yes sure just a sec

Davor Maric · Answer

``` override fun validateAdminWithCredentials username String password String Single lt Authenticator gt return Single zip checkIfPopulated findAdministratorInDatabase username password BiFunction lt Boolean Boolean Pair lt Boolean Boolean gt gt t1 t2 gt Pair t1 t2 flatMap pair gt val returnValue = if pair first Single just Pair pair second false else Single fromCallable local adminDao insert createDefaultAdmin map Pair pair second true returnValue map Authenticator it first it second subscribeOn <http Schedulers io|Schedulers io> ```

Davor Maric · Answer

what this does is this checks if admin table is populated FALSE create default administrator and notify user about it TRUE validate administrator TRUE notify user about success FALSE notify user about failure OnERROR trigger onError for fail I O communication

Davor Maric · Answer

< gildor>

Davor Maric · Answer

I stand corrected for andThen Thanks slightly smiling face

Davor Maric · Answer

Is andThen executed after Completable emits complete only or is it executed after emitter complete or emitter error