gistfile1.scala

trait WithContext {
  var ctx = null
  def setContext(c:Context): Unit = if (ctx == null) {
    ctx = c
  } else {
    sys.error("already set")
  }
  def fromContext[T](k:String):T = if (ctx == null) {
    sys.error("premature access")
  } else {
    ctx.get(k).asInstanceOf[T]
  }
}

class MyBundle extends WithContext {
  lazy val foo = fromContext[Int]("foo")
  lazy val bar = fromContext[Widget]("bar")
  lazy val qux = fromContext[Double]("qux")

  def onCreate(c:Context) {
    setContext(c)
    ...
  }

  ...
}