Using Scala extractor with List filter and find

gistfile1.txt

class Member(val id: String, val programId: Long)

class Program3Member(val memberId: String, val program: String)
object Program3Member {
  def unapply(c: Member): Option[Member] = { if(c.programId == 3L) Some(c) else None }
}

val pete = new Member("12345", 9L)
val steve = new Member("67891", 3L)
val janet = new Member("23458", 3L)
val dave = new Member("78934", 6L)
val someMembers = List(pete, steve, janet, dave)

//it is a bit klunky
val membersInProgram3 = someMembers filter { _ match { case Program3Member(n) => true case _ => false } }
val firstMemberInProgram3 = someMembers find { _ match { case Program3Member(n) => true case _ => false } }

//extractors have much better support in a for-comprehension
for(Program3Member(n) <- someMembers) { println(n.id) }

//especially notable - we can replace the membersInProgram3 declaration with this
val membersInProgram3 = for(Program3Member(n) <- someMembers) yield n