command pattern in Scala

App.scala

package com.mycode

object App {
  def main(args : Array[String]) {
   val receiver = new Receiver

    val task = new ConcreteCommandTask(receiver)
    val play = new ConcreteCommandTaskPlay(receiver)

    val invoker = new Invoker
    invoker.setCommand(task)
    invoker.executeCommand

    invoker.setCommand(play)
    invoker.executeCommand
  }
}

class Receiver {
  def action1 {
    println("掃除をする")
  }

  def action2 {
    println("選択をする")
  }

  def action3 {
    println("電話料金を支払う")
  }

  def action4 {
    println("水道料金を支払う")
  }
}


abstract class Command {
  protected var receiver:Receiver
  def execute{}
}


class ConcreteCommandTask(var receiver:Receiver) extends Command {
  override def execute {
    this.receiver.action1
    this.receiver.action2
  }
}

class ConcreteCommandTaskPlay(var receiver:Receiver) extends Command {
  override def execute {
    this.receiver.action3
    this.receiver.action4
  }
}

class Invoker {
  private var command:Command = null

  def getCommand = command

  def setCommand(command:Command) {
    this.command = command
  }
  def executeCommand {
    this.command.execute
  }
}