Calling object methods polymorphically

Question

class A 

class B extends A

object B {
  def createSidekick = new B
}

class C extends A

object C {
  def createSidekick = new C
}

object foo {
  def bar[T <: C] = {
    // T.createSidekick
  }
}

In foo.bar, I would like to call methods from the given object. However, Scala does not allow to extend objects, so there is no obvious way of accomplishing this. What is the best way to accomplish this sort of behaviour?

Rado Buransky · Accepted Answer · 2014-01-15 04:56:23Z

1

Something like this?

class A

class B extends A

trait Sidekicker[T <: A] {
  def createSidekick: T
}

object B extends Sidekicker[B] {
  def createSidekick = new B
}

class C extends A

object C extends Sidekicker[C] {
  def createSidekick = new C
}

object foo {
  def bar(s: Sidekicker[_]) = s.createSidekick

  val b = bar(B)
  val c = bar(C)
}

answered Jan 15, 2014 at 4:56

Rado Buransky

3,29420 silver badges28 bronze badges

Sign up to request clarification or add additional context in comments.

6 Comments

ojmb Over a year ago

I was hoping there might be some elegant solution where I just use the Type parameter

Rado Buransky Over a year ago

Do you mean bar[B] instead of bar(B)? Well, that's just a matter of personal taste whether you like more rounded shapes or sharp ones.

senia Over a year ago

@user1225310: You could use type classes like this: link to pastebin.com. Note that you could define implicit val for Sidekicker[T] not only in companion object.

senia Over a year ago

@RadoBuransky: you could add typeclasses implementation as alternative option to your answer.

Rado Buransky Over a year ago

@senia: Interesting, thanks. When would you recommend "mine" and where "your" approach?

|

Collectives™ on Stack Overflow

Calling object methods polymorphically

1 Answer 1

6 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

6 Comments

Your Answer

Sign up or log in

Post as a guest

Related