title: Scala Listener/Observer
body: <p>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. </p>
  
  <p>Is there a more Scala-like way to do this? Should I be using this pattern in Scala, or is there something else baked into the language I should be taking advantage of? </p>