Scala Listener/Observer

Question

Typically, in Java, when I\'ve got an object who\'s providing some sort of notification to other objects, I\'ll employ the Listener/Observer pattern.

Is there a mor

Answer 1

trait Observer[S] {
     def receiveUpdate(subject: S);
}

trait Subject[S] {
     this: S =>
     private var observers: List[Observer[S]] = Nil
     def addObserver(observer: Observer[S]) = observers = observer :: observers

     def notifyObservers() = observers.foreach(_.receiveUpdate(this))
}

This snippet is pretty similar to what one would find in Java with some Scala features. This is from Dean Wampler's blog - http://blog.objectmentor.com/articles/2008/08/03/the-seductions-of-scala-part-i

This uses some Scala features such as generics as denoted by the [S], traits which are like Java interfaces but more powerful, :: to prepend an observer to the list of observers, and a foreach with the parameter using an _ which evaluates to the current observer.