I have `A` class like this: ```data class A(val listOfB: List<B>)``` And `B` is a sealed inter...

# android

[AmrJyniat]

I have A class like this:

data class A(val listOfB: List<B>)

And B is a sealed interface which has multiple children like this:

sealed interface B
object C: B
object D: B
.....

Ok, now I have a list of A and each item holds a list of B, what I want is to return the A list contains only the C items in each B list.
I mean that I want to remove each item that isn't C from each B list in A list

What is the straight forward way to do that?

[Javier]

val cList = aList.flatMap { it.filterIsInstance<C>() }

[AmrJyniat]

Sorry for the unclear question at first, I updated the question, is it clear now?

[Javier]

aList.filter { a -> a.listOfB.all { b -> b is C } }

[AmrJyniat]

Doesn't work, This will not return the A item if wasn't all B items type is C, but what I want to filter is each B list not the A list.

[Javier]

Then you need to use copy or arrow optics probably

[Javier]

val filteredAList: List<A> = aList.map { a -> a.copy(listOfB = a.listOfB.filterIsInstance<C>()) }

[AmrJyniat]

Yeah, that works, Thank you!