Scala case class private constructor but public apply method

Question

If I have the following case class with a private constructor and I can not access the apply-method in the companion object.

case class Meter private (m: Int)  val m = Meter(10) // constructor Meter in class Meter cannot be accessed... 

Is there a way to use a case class with a private constructor but keep the generated apply-method in the companion public?

I am aware that there is no difference (in my example) between the two options:

val m1 = new Meter(10) val m2 = Meter(10) 

but I want to forbid the first option.

-- edit --

Surprisingly the following works (but is not really what i want):

val x = Meter val m3 = x(10) // m3  : Meter = Meter(10) 

Answer 1

Here's the technique to have a private constructor and a public apply method.

trait Meter {   def m: Int }  object Meter {      def apply(m: Int): Meter = { MeterImpl(m) }   private case class MeterImpl(m: Int) extends Meter { println(m) } }  object Application extends App {   val m1 = new Meter(10) // Forbidden   val m2 = Meter(10) } 

Background information private-and-protected-constructor-in-scala

Answer 2

It seems the requested behavior (private constructor but public .apply) may be the way Scala 2.12 implements these.

I came to this from the opposing angle - would like a private case class constructor also block the .apply method. Reasons here: https://github.com/akauppi/case-class-gym

Interesting, how use cases differ.