Question

Is there some standard way in Scala of specifying a function that does nothing, for example when implementing a trait? This works:

trait Doer {
  def doit
}

val nothingDoer = new Doer {
  def doit = { }
}

But perhaps there is some more congenial way of formulating nothingDoer?

Edit Some interesting answers have appeared, and I add a little to the question in response. First, it turns out that I could have used a default implementation in Doer. Good tip, but you don’t always want that. Second, apparently a more idiomatic way of writing is:

val nothingDoer = new Doer {
  def doit { }
}

Third, although nobody suggested exactly that, I found that this also seems to work:

val nothingDoer = new Doer {
  def doit = Unit
}

Is this a good alternative?

(The “:Unit” that a few people suggested does not really add anything, I think.)

Answer 1

Since your return type is Unit, it’s conventional not to use the =

val nothingDoer = new Doer {
  def doit {}
}