Question

I’d like to use a timer in a Scala Swing application. I can use the Java version, only it means I have to implement the ActionListener interface. I’d rather use the Scala Publishers / Reactors model for consistency, so I can have things that listenTo the timer.

Here’s what I tried:

class ScalaTimer(time: Int) extends Component {
  val t = new javax.swing.Timer(time, new java.awt.event.ActionListener {
    def actionPerformed(e: java.awt.event.ActionEvent) {
      publish(new scala.swing.event.ActionEvent(this))
    }
  })
  def start() {t.start()}
  def stop() {t.stop()}
  // etc

}

Doesn’t work because this refers to the the ActionListener rather than the ScalaTimer class.

Also I probably shouldn’t be extending Component… I tried this because I get the Publisher / Reactor functionality, but it doesn’t really make sense. Should I do something like this instead? If so, are there other traits I need to include, and how do I know which methods I have to implement?

 class ScalaTimer extends javax.swing.Timer with Publisher {

(My IDE immediately flags “Missing arguments for method Timer(Int, ActionListener)” which seems a bit weird since I haven’t invoked a method.)

Answer 1

The canonical way to do this is to introduce an alias at the top of the thing you want to refer to (usually self unless that’s already taken):

class ScalaTimer(time: Int) extends Component {
  self =>
  val t = ...
    publish(new scala.swing.event.ActionEvent(self))
  ...