How to define object inside sealed generic hierarchy ``` sea kotlinlang #getting-started

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Title

a

ar-g

08/10/2017, 12:51 PM

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>()
}

m

marstran

08/10/2017, 12:54 PM

You need to specify a

for your objects.

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.

a

ar-g

08/10/2017, 12:55 PM

no, type parameters not allowed

m

marstran

08/10/2017, 12:56 PM

The

has to be an actual class/interface here:

object LoadingFirstPage : PaginationViewState<T>()

No type parameters allowed? What do you mean? You have specified

PaginationViewState

with a type parameter.

a

ar-g

08/10/2017, 12:57 PM

not allowed in this statement

object LoadingFirstPage<T>: PaginationViewState<T>()

m

marstran

08/10/2017, 12:57 PM

That doesn't work because there is only one instance of

LoadingFirstPage

. It can't take parameters.

Maybe

LoadingFirstPage

should be a class then?

a

ar-g

08/10/2017, 12:58 PM

that is what I did😀

m

marstran

08/10/2017, 1:09 PM

It looks like that should be the correct solution for you looking at your example.

is the type of data that the view state holds, so

LoadingFirstPage

and

LoadingPage

are classes, not objects.

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.

👍 1

a

ar-g

08/10/2017, 1:21 PM

yes, it is meaningless since I can't define class with desired type

PaginationViewState<AdModel> =PaginationViewState.LoadingFirstPage

. I'll stick with regular classes probably

m

marstran

08/10/2017, 1:46 PM

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

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