CODEWITHSUNDEEP
androidkotlinsealed-class
Hayk Mkrtchyan
Hayk Mkrtchyan

Reputation: 3265

Android - How to make sealed class extend other sealed class?

I have a sealed interface for my UIState.

sealed interface UIState<out T> {
    object ShowLoading : UIState<Nothing>
    object ShowEmptyData : UIState<Nothing>
    data class ShowData<out T>(val data: T) : UIState<T>
    data class ShowError(val errorUIState: ErrorUIState) : UIState<Nothing>
}

This is general for most of the screens in my application, but let's take I have a search screen and along with this states I need one more state

object ShowNoSearchResult: UIState<Nothing>

If I add this state inside UIState sealed interface, in all the screens I need to handle this state, but I need it only in the search screen. As a solution, I tried to create a new sealed interface and extend the UIState.

sealed interface SearchUIState<out T>: UIState<T> {
    object ShowNoSearchResult: SearchUIState<Nothing>
}

Now the issue is that I can't call any UIState class using my SearchUIState. The ShowLoading, ShowEmptyData, etc. are not available if I use SearchUIState. What I want is to use SearchUIState to handle all the states of the SearchUIState and its parent states as well? Is there a way to do this without code duplication?

P.S. Actually using the parent sealed interface I can return the child sealed interface state as well. The thing is that still when I handle parent sealed interface states using when, it requires to handle also all the child sealed interface states.

Upvotes: 5

Views: 1598

Answers (1)

Tenfour04
Tenfour04

Reputation: 93834

You can make each of the UIState children also implement SearchUIState, and you can change SearchUIState to not be a subtype of UIState.

sealed interface UIState<out T> {
    object ShowLoading : UIState<Nothing>, SearchUIState<Nothing>
    object ShowEmptyData : UIState<Nothing>, SearchUIState<Nothing>
    data class ShowData<out T>(val data: T) : UIState<T>, SearchUIState<T>
    data class ShowError(val errorUIState: ErrorUIState) : UIState<Nothing>, SearchUIState<Nothing>
}

sealed interface SearchUIState<out T> {
    object ShowNoSearchResult: SearchUIState<Nothing>
}

Upvotes: 1

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