lazy.scala

class Generator {
  // ...
}

object GeneratorUser {
  
  def getGenerator(implicit seed: Int): Generator {
    val gen = makeGenerator(seed)
    gen.doSomethingElse() // Will error if called more than once, globally
    gen
  }
  
}

class GeneratorUser {
  
  implicit lazy val seed = getSeed()
  
  override def getSeed() {
    // ...
  }
  
}