UnapplySeq Example

apply_unapply.scala

/**
 * For regular parameters / fixed arity these are the apply constructs and unapply de-structures:
 */
object S {
  def apply(a: A):S = ... // makes a S from an A
  def unapply(s: S): Option[A] = ... // retrieve the A from the S
}
val s = S(a)
s match { case S(a) => a } 

/**
 * For repeated parameters / variable arity these are the apply constructs and unapplySeq de-structures:
 */
object M {
  def apply(a: A*): M = ......... // makes a M from an As.
  def unapplySeq(m: M): Option[Seq[A]] = ... // retrieve the As from the M
}
val m = M(a1, a2, a3)
m match { case M(a1, a2, a3) => ... } 
m match { case M(a, as @ _*) => ... } 

//For example... 
object Names {
  def unapplySeq(name: String): Option[(String, String, Array[String])] = {
    val names = name.trim.split(" ")
    if (names.size < 2) None
    else Some((names.last, names.head, names.drop(1).dropRight(1)))
  }
}

def greet(fullName: String) = fullName match {
  case Names(lastName, firstName, a) => "Good morning, " + firstName + " " + lastName + "!"
  case _ => "Welcome! Please make sure to fill in your name!"
}

greet("John Michael Doe") // res0: String = Good morning, John Doe!