第22章：Scalaの抽出子 ref: http://qiita.com/f81@github/items/109dbe953dac516bd71a

file1.txt

$ scalac User.scala
$ scala  scala User
赤石 剛次

file10.scala

scala> class ApplyClass(val message: String); object ApplyClass { def apply(message: String): ApplyClass = { new ApplyClass(message) } }
defined class ApplyClass
defined module ApplyClass

scala> ApplyClass("乱坊少佐")
res0: ApplyClass = ApplyClass@43679ffd

file11.scala

def apply[A](elems: A*): Seq[A]

file12.scala

Seq(1, 2, 3)

file2.scala

class User(private val firstname: String, private val lastname: String)

file3.scala

object User {

  def unapply(user: User) = Option((user.firstname, user.lastname))
}

file4.scala

  def main(args: Array[String]): Unit = {
    val user = new User("剛次", "赤石")

    user match {
      case User(firstname, lastname) => println(lastname + " " + firstname)
      case _ => println("Not user.")
    }
  }

file5.scala

object User1 {

  def main(args: Array[String]): Unit = {
    val user = new User("剛次", "赤石")
    val User(firstname, lastname) = user

    println(lastname + " " + firstname)
  }

}

file6.scala

val seq = Seq(1, 2, 3, 4)
val Seq(x, y , _*) = seq

file7.scala

scala> object ApplyTest { def apply(message: String) { println(message) } }

file8.scala

scala> ApplyTest.apply("乱坊少佐")
乱坊少佐

file9.scala

scala> ApplyTest("乱坊少佐")
乱坊少佐

User.scala

import scala.Option

class User(private val firstname: String, private val lastname: String)

object User {

  def unapply(user: User) = Option((user.firstname, user.lastname))

  def main(args: Array[String]): Unit = {
    val user = new User("剛次", "赤石")

    user match {
      case User(firstname, lastname) => println(lastname + " " + firstname)
      case _ => println("Not user.")
    }
  }

}