Sorry if I'm bothering, but I sometimes encounter ...

# javascript

[Hildebrandt Tobias]

Sorry if I'm bothering, but I sometimes encounter these "double types".
For example TanStack Table has the Updater which is defined like this:

sealed external interface Updater<T> /* T | ((old: T) -> T) */

inline fun <T> Updater(
    source: T,
): Updater<T> =
    unsafeSpecialCast(source)

inline fun <T> Updater(
    noinline source: (old: T) -> T,
): Updater<T> =
    unsafeSpecialCast(source)

I know I can create these using functionalUpdate() but how do I consume them?
Currently I do

this.onSortingChange = { newSorting ->
    setSorting(newSorting.unsafeCast<SortingState>())
}

but it feels kind of wrong.
What is correct way to consume such an Updater ?

[Erik van Velzen]

this.onSortingChange = Updater<SortingState> { newSorting ->
    setSorting(newSorting)
}

Does this work?

[Hildebrandt Tobias]

Sadly, no:

[Hildebrandt Tobias]

The compiler suggestion 😅

[Hildebrandt Tobias]

Okay this works, but it still doesn't look right this mimics the doc though (https://tanstack.com/table/v8/docs/guide/pagination):

useReactTable<T>(
    options = jso {
        val (pagination, setPagination) = states.pagination // StateInstance<PaginationState>
        
        this.state = jso<TableState> {
            this.pagination = pagination
        }
        
        this.onPaginationChange = unsafeSpecialCast(setPagination) 
    }
)

[turansky]

We have invalid declaration for Updater in fact

[turansky]

If you use Kotlin Wrappers and you need unsafeCast or asDynamic :
1. Probably you need it without reason, please check one more time
2. It can be typization error in wrappers (current case)

[turansky]

@Hildebrandt Tobias could you please report the problem, I will fix it 😎

[Hildebrandt Tobias]

In YouTrack or Kotlin-Wrapper Issues?

[turansky]

Kotlin Wrappers please

[Hildebrandt Tobias]

Will do

[Hildebrandt Tobias]

https://github.com/JetBrains/kotlin-wrappers/issues/2779

[turansky]

Fix released in Kotlin Wrappers 2025.5.0 😎

[Hildebrandt Tobias]

Hey sorry to come back to this. The OnChangeFn works. (Thanks again!)
But I wonder how I handle these "double types" in general. They do come up often.
For example the Updater from onPaginationChange in TanStackTable can be (T) -> T or just T.
I found isExternalObject(a, b) but it's internal so I can't use it.
I could also do

jsTypeOf(updater) == "function")

but is this really the intended way?

[Hildebrandt Tobias]

I guess this works, but is it meant to be that way?

onPaginationChange = OnChangeFn { updaterOrValue: Updater<PaginationState> ->
    val newValue: PaginationState = if (jsTypeOf(updaterOrValue) == "function") {
        val fn = updaterOrValue.unsafeCast<(PaginationState) -> PaginationState>()
        fn(pagination)
    } else {
        updaterOrValue.unsafeCast<PaginationState>()
    }
    println("New value: ${JSON.stringify(newValue)}")
},

[turansky]

Only in case when you had no frameworks

[turansky]

Every framework (React in our case) should provide fine adapter.

[Hildebrandt Tobias]

I don't quite understand.
Is there such an adapter in the react wrappers?
Also is there a way to access the typeCheckUtils ?
There seem to be some really nice tools for edge cases like JsEqEqEq.

[turansky]

I don't quite understand.

Is there such an adapter in the react wrappers?

In kotlin-tanstack-react-table

[turansky]

Also is there a way to access the typeCheckUtils ?

There seem to be some really nice tools for edge cases like JsEqEqEq.

Is there any links with examples?

[Hildebrandt Tobias]

About kotlin-tanstack-react-table isn't that this here, what I already use?:

[turansky]

In React part (of TanStack Table) we provide adapters for React types

[Hildebrandt Tobias]

Maybe to clarify, I already do this everywhere else:

onSortingChange = OnChangeFn(setSorting),
onGroupingChange = OnChangeFn(setGrouping),
onColumnVisibilityChange = OnChangeFn(setColumnVisibility),
onGlobalFilterChange = OnChangeFn(setGlobalFilter),
onColumnFiltersChange = OnChangeFn(setColumnFilters),

And it works fine, no problems. But it doesn't let me do what I want in the onSomething function.
What if I don't want to just pass a StateSetter? What if I want to do something beforehand?
Or manipulate the value?

[Hildebrandt Tobias]

If the only functionality I can cover with onPaginationChange is passing a StateSetter.
Isn't it actually a setPaginationStateInstance instead? And not "do something when pagination changes".