early-definition.scala

trait A {
  val count: Int
  val elements: Array[String] = new Array(count)
}

class C extends A {
  override val count = 10
}

val c = new C
println(c.elements.length) // Surprise, it's 0.


// -----------------------------------------------------------------------------
// Using an early definition.
// -----------------------------------------------------------------------------

trait A {
  val count: Int
  val elements: Array[String] = new Array(count)
}

class C extends { // early definition
  override val count = 10
} with A

val c = new C
println(c.elements.length) // 10

• http://www.scala-lang.org/files/archive/spec/2.11/05-classes-and-objects.html#early-definitions
• http://stackoverflow.com/q/16348541/58808
• http://stackoverflow.com/q/4712468/58808