Scala - Chaining traits

ChainingTraits.scala

trait Irrelevant {}


trait Base {
  def text: String = "Base"

  def enter: () => Any =
    () => {
      println("enter: Some logic")
    }

  def embed: () => Any =
    () => {
      println("embed: Some logic")
    }

  def leave: () => Any =
    () => {
      println("leave: Some logic")
    }

}


trait A extends Irrelevant with Base {
  override def text: String = "A extends " + super.text

  override def enter: () => Any =
    () => {
      super.enter()
      println("enter: Some logic added by A")
    }

  override def embed: () => Any =
    () => {
      println("embed: A before")
      super.embed()
      println("embed: A after")
    }

  override def leave: () => Any =
    () => {
      println("leave: Some logic added by A")
      super.leave()
    }
}


trait B extends Irrelevant with Base {
  override def text: String = "B extends " + super.text

  override def enter: () => Any =
    () => {
      super.enter()
      println("enter: Some logic added by B")
    }

  override def embed: () => Any =
    () => {
      println("embed: B before")
      super.embed()
      println("embed: B after")
    }

  override def leave: () => Any =
    () => {
      println("leave: Some logic added by B")
      super.leave()
    }
}

class TestCase extends Irrelevant with Base with A with B {
  println("========================================")
  println(text)
  println("----------------------------------------")
  enter()
  println("----------------------------------------")
  embed()
  println("----------------------------------------")
  leave()
  println("========================================")
}

object Main {
  def main(args: Array[String]): Unit = {
    new TestCase
  }
}

// prints:
//
// ========================================
// B extends A extends Base
// ----------------------------------------
// enter: Some logic
// enter: Some logic added by A
// enter: Some logic added by B
// ----------------------------------------
// embed: B before
// embed: A before
// embed: Some logic
// embed: A after
// embed: B after
// ----------------------------------------
// leave: Some logic added by B
// leave: Some logic added by A
// leave: Some logic
// ========================================