Often when I try to handle generics I run into thi...

# announcements

[Fabio]

Often when I try to handle generics I run into this casting situation, which generates a warning that I don't understand:

abstract class TodayDynamicModel<V : View> : BardeenListUiModel() {

    fun asTodayDynamicModel() = this as TodayDynamicModel<View> // --> Unchecked cast: TodayDynamicModel<V> to TodayDynamicModel<View>
}

Isn't V guaranteed to be of type View ?

[Kroppeb]

This is only valid if you use TodayDynamicModel<out V:View>

[Fabio]

@Kroppeb
also, then I can't write

abstract class TodayDynamicModel<out V : View> : BardeenListUiModel() {
    abstract fun bindView(view: V) // Type parameter V is declared as 'out' but occurs in 'in' position in type V

And if I do <in V: View> I can't do abstract fun buildView(context: Context): V?

[Fabio]

full class for disclosure (it's a variation of RecyclerView btw, and I changed the name since original post)

abstract class BardeenDynamicRecyclerViewModel<V : View> : BardeenListUiModel() {

    abstract fun bindView(view: V?)

    abstract fun buildView(context: Context): V?

    @Suppress("UNCHECKED_CAST")
    fun asTodayDynamicModel() = this as BardeenDynamicRecyclerViewModel<View>

    fun buildAndBindView(context: Context): V? {

        return buildView(context)
            .also {
                bindView(it)
            }
    }
}

[Fabio]

found the solution, I added out V:View in fun asTodayDynamicModel() = this as BardeenDynamicRecyclerViewModel<out View> and in a bunch of places that call asTodayDynamicModel.