Filtering a Scala List by type

Question

I have a class structure like this

abstract class A
class B extends A
class C extends A
class D extends A
class E extends A

and I have a co

Answer 1

flatMap that shit! (as they say):

scala> val ys = xs flatMap {
     |   case _: B | _: C => None
     |   case other => Some(other)
     | }
ys: List[A] = List(D@7ecdc97b, E@2ce07e6b, E@468bb9d1)

In your case you were getting a List[ScalaObject] because ScalaObject is the least upper bound of None, D, and E.

Answer 2

Formulating problems as questions seems to be a pretty good way of solving them :) My question actually provides the answer - just filter by subtype:

val ys = xs filterNot(List(classOf[B], classOf[C]) contains _.getClass)

Answer 3

collect can be used to filter values on which the function is defined:

Get all values of type A:

xs.collect { case a: A => a }

Get all values except B and C:

xs diff xs.collect { case x@(_: B | _: C) => x }