How to define object inside sealed generic hierarc...

# getting-started

[ar-g]

How to define object inside sealed generic hierarchy?

sealed class PaginationViewState<T> {
    object LoadingFirstPage: PaginationViewState<T>()//doesn't work
    object LoadingPage: PaginationViewState<T>()//doesn't work

    data class DataLoaded<T>(val data: List<T>): PaginationViewState<T>()
    data class DataLoadedFromCache<T>(val data: List<T>): PaginationViewState<T>()
    data class Failure<T>(val e: Throwable): PaginationViewState<T>()
}

[marstran]

You need to specify a T for your objects.

[marstran]

By the way, after Kotlin 1.1, you don't need to nest the classes and objects inside the sealed class. They just have to be in the same file.

[ar-g]

no, type parameters not allowed

[marstran]

The T has to be an actual class/interface here: object LoadingFirstPage : PaginationViewState<T>()

[marstran]

No type parameters allowed? What do you mean? You have specified PaginationViewState with a type parameter.

[ar-g]

not allowed in this statement object LoadingFirstPage<T>: PaginationViewState<T>()

[marstran]

That doesn't work because there is only one instance of LoadingFirstPage. It can't take parameters.

[marstran]

Maybe LoadingFirstPage should be a class then?

[ar-g]

that is what I did😀

[marstran]

It looks like that should be the correct solution for you looking at your example. T is the type of data that the view state holds, so LoadingFirstPage and LoadingPage are classes, not objects.

[marstran]

I see you are writing on the StackOverflow post that using Any is what you were looking for. I really don't think you should do that. You are losing type information that you don't have to lose.

[ar-g]

yes, it is meaningless since I can't define class with desired type PaginationViewState<AdModel> =PaginationViewState.LoadingFirstPage. I'll stick with regular classes probably

[marstran]

You can still have (and you should have) a sealed class hierarchy though.