Question

I encountered this syntax in someone else’s Scala code, and don’t remember reading about it:

val c  = new C { i = 5 }

It appears that the block after the new C is equivalent to:

val c = new C
c.i = 5

assuming a class definition like:

class C {
  var ii = 1
  def i_=(v: Int) { ii = v }
  def i = ii
}

What is this syntax called in Scala? I want to read more about it, but I can’t find it described in Programming in Scala or elsewhere.

Answer 1

You are instantiating an anonymous subclass of C.

It is not equivalent to the code you’ve shown — try calling getClass on the two instances called c in your snippets.