CoffeePot Cake

gistfile1.scala

object CoffeePot extends App {
  ComponentRegistry.coffeeWarmer.trigger
}

trait OnOffDevice {
  def on: Unit
  def off: Unit
}

trait SensorDevice {
  def isCoffeePresent: Boolean
}

trait Heater extends OnOffDevice {
  def on = println("heater.on")
  def off = println("heater.off")
}

trait PotSensor extends SensorDevice {
  def isCoffeePresent = true
}

trait Warmer {
  this: OnOffDevice with SensorDevice =>

  def trigger = {
    if (isCoffeePresent) on
    else off
  }
}

object ComponentRegistry {
  val coffeeWarmer = new Warmer with PotSensor with Heater
}