Private and protected constructor in Scala

Question

I\'ve been curious about the impact of not having an explicit primary constructor in Scala, just the contents of the class body.

In particular, I suspect that the pr

Answer 1

Aleksander's answer is correct, but Programming in Scala offers an additional alternative:

sealed trait Foo {
 // interface
}

object Foo {
  def apply(...): Foo = // public constructor

  private class FooImpl(...) extends Foo { ... } // real class
}

Answer 2

You can declare the default constructor as private/protected by inserting the appropriate keyword between the class name and the parameter list, like this:

class Foo private () { 
  /* class body goes here... */
}