Example of stackable traits in Scala

StackableTraits.scala

type Payload = Array[Byte]

trait Driver {
  def send(payload: Payload)
}

//a component which depends on Driver interface
class Sender(val driver: Driver){
  def send(message: String) = driver.send(message.getBytes)
}
object Sender{
  def apply(driver: Driver): Sender = new Sender(driver)
}

//3rd-party implementation of the Driver
class NetworkDriver extends Driver{
  override def send(payload: Payload): Unit = {
    println("..transferring..")
    Thread.sleep(50)
  }
}

//now developers decided to log the payload
trait PayloadLogging extends Driver {
  abstract override def send(payload: Payload): Unit ={
    println(s"sending the payload: ${payload.mkString}")
    super.send(payload)
  }
}

//and measure the time spent in method
trait TimeLogging extends Driver {
  abstract override def send(payload: Payload): Unit ={
    val start = System.currentTimeMillis()
    super.send(payload)
    print(s"time spent: ${System.currentTimeMillis() - start}ms")
  }
}

//legacy implementation
Sender(new NetworkDriver).send("hello")
/*output:
..transferring..
*/

//mixing in payload logging
Sender(new NetworkDriver with PayloadLogging).send("hello")
/*output:
sending payload: 104101108108111
..transferring..
*/

//mixing in payload and time logging
Sender(new NetworkDriver with PayloadLogging with TimeLogging).send("hello")
/*output:
sending payload: 104101108108111
..transferring..
time spent: 56ms
*/

StackableTraitsMixinOrder.scala

trait Writer {
  def write(msg: String)
}

class ConsoleWriter extends Writer {
  override def write(msg: String): Unit = println(msg)
}

trait UppercaseFilter extends Writer {
  abstract override def write(msg: String): Unit = {
    super.write(msg.toUpperCase)
  }
}

trait AdFilter extends Writer {
  abstract override def write(msg: String): Unit = {
    super.write(msg.replace("ad", "[ad blocked]"))
  }
}

class Publisher(val writer: Writer){
  def publish(msg: String) = writer.write(msg)
}
object Publisher{
  def apply(writer: Writer): Publisher = new Publisher(writer)
}

Publisher(new ConsoleWriter).publish("my awesome ad")
/*output:
my awesome ad
*/

Publisher(new ConsoleWriter with UppercaseFilter).publish("my awesome ad")
/*output:
MY AWESOME AD
*/

Publisher(new ConsoleWriter with UppercaseFilter with AdFilter).publish("my awesome ad")
/*output:
MY AWESOME [AD BLOCKED]
*/

Publisher(new ConsoleWriter with AdFilter with UppercaseFilter).publish("my awesome ad")
/*output:
MY AWESOME AD

ad replacement is case sensistive, so after UppercaseFilter is Applied
there's no 'ad' anymore
*/