CODEWITHSUNDEEP
scala
Ian
Ian

Reputation: 1304

Stacking traits and abstract classes with overrides

Let's say I have the following code where I allow hybrid beings and because someone can mix and match species (e.g. just have pure humans or pure aliens), I'd like to have a method that explains what's been 'mixed in', which is called say:

trait Person {

  def say(): Unit

}

trait Human {

  def say(): Unit = println("Hi, I am a human")
}

trait Dude extends Human {

  override def say(): Unit = {
    super.say()
    println("Duuude!")
  }
}

abstract class Alien(msg: String) extends Person {

  def say(): Unit = println(s"Hi, I'm an alien: $msg")
}

class Hybrid(name: String) extends Alien("bleep") with Dude // does not work!

val someone = new Hybrid("John")
someone.say()

This does not compile because:

error: overriding method say in class Alien of type ()Unit;
method say in trait Dude of type ()Unit cannot override a concrete member without a third member that's overridden by both (...)

Is it possible to have someone.say() display the following?

Hi, I'm am a human
Duuude!
Hi, I'm an alien: bleep

I have thought about creating a special class that already mixes in both traits/classes but how would I then go about accessing the respective say methods, as obviously super.say will be ambiguous.

Upvotes: 0

Views: 64

Answers (2)

Alexey Romanov
Alexey Romanov

Reputation: 170713

class Hybrid(name: String) extends Alien("bleep") with Dude {
  override def say() = {
    super[Dude].say()
    super[Alien].say()
  }
}

Upvotes: 6

Rakshith
Rakshith

Reputation: 664

So Basically the class Hybrid doesnt know which say method needs to be overridden. This could be resolved by changing the method name . U can try this 

trait Person {

  def say(): String

 }

  trait Human {
  def sayHuman: String = ("Hi, I am a human")
 }

trait Dude extends Human {

 override def sayHuman(): String = {
super.sayHuman +"Duuude!"
 }
}

 abstract class Alien(msg: String) extends Person {

  def say(): String= "Hi, I'm an alien:"+msg
}


class Hybrid(name: String) extends Alien("bleep") with Dude{
override def toString:String= super.say+"\n"+super.sayHuman
}

Upvotes: 0

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