title: Private and protected constructor in Scala
body: <p>I've been curious about the impact of not having an explicit primary constructor in Scala, just the contents of the class body.</p>
  
  <p>In particular, I suspect that the private or protected constructor pattern, that is, controlling construction through the companion object or another class or object's methods might not have an obvious implementation. </p>
  
  <p>Am I wrong? If so, how is it done?</p>