Given two `Either lt Left Right gt ` where `Left` is `sealed

Question

Given two `Either lt Left Right gt ` where `Left` is `sealed interface Left A B ` I want `Right` if one of the two Either is Right otherwise the Either which `Left` is `A` if any In other words the priority is `Right gt Left A gt whatever` don t really need `Left B` Which would be the best way to achieve that

Davide Giuseppe Farella · Answer

Specifically I have ```sealed interface GetAccountError data class NetworkError GetAccountError object NotConnected GetAccountError val tmdbEither Either lt GetAccountError Account gt val traktEither Either lt GetAccountError Account gt ``` I want `Account` if any otherwise `AccountError` if any otherwise I know no account is connected

Davide Giuseppe Farella · Answer

So far this is the cleanest way I found ```tmdbAccountUiModelEither fold ifLeft = accountError gt if accountError is GetAccountError Network return combine ManageAccountState Account Error message = networkErrorMapper toMessage accountError networkError ifRight = account gt return combine ManageAccountState Account Connected account traktAccountUiModelEither fold ifLeft = accountError gt if accountError is GetAccountError Network return combine ManageAccountState Account Error message = networkErrorMapper toMessage accountError networkError ifRight = account gt return combine ManageAccountState Account Connected account return combine ManageAccountState Account NotConnected```

simon.vergauwen · Answer

I am not sure what `return combine` is doing here thinking face If I understand correctly with `1 2 6 alpha 28` you can write ```fun GetAccountError Network toManageError = ManageAccountState Account Error message = networkErrorMapper toMessage accountError networkError tmdbEither recover e gt if e is NetworkError raise e toManageError else traktEither recover if e is NetworkError raise e toManageError else raise ManageAccountState Account NotConnected map ManageAccountState Account Connected account ``` Or before ```fun GetAccountError Network toManageError = ManageAccountState Account Error message = networkErrorMapper toMessage accountError networkError tmdbEither handleErrorWith e gt if e is NetworkError e toManageError left else traktEither handleErrorWith if e is NetworkError e toManageError left else ManageAccountState Account NotConnected left map ManageAccountState Account Connected account ```

Davide Giuseppe Farella · Answer

Thanks that s seems perfect I ll try it tomorrow P s `return combine` just because I m inside the lambda of a `combine` ```combine getTmbdAccount getTraktAcoount Code above ```

simon.vergauwen · Answer

Right okay then I understood it correctly I think the code above should work relaxed

Davide Giuseppe Farella · Answer

Implemented your solution and did some refactoring moved to domain Looks so neat ```operator fun invoke Flow lt Either lt GetAccountError Account gt gt = combine getTmdbAccount getTraktAccount tmdbAccountEither traktAccountEither gt check tmdbAccountEither isLeft || traktAccountEither isLeft Both accounts are connected this is not supported tmdbAccountEither handleErrorWith tmdbError gt traktAccountEither handleErrorWith traktError gt if tmdbError is GetAccountError Network tmdbError left else traktError left ```