I'm trying to find a cleaner alternative (that is idiomatic to Scala) to the kind of thing you see with data-binding in WPF/silverlight data-binding - that is, implementing INotifyPropertyChanged. First, some background:

In .Net WPF or silverlight applications, you have the concept of two-way data-binding (that is, binding the value of some element of the UI to a .net property of the DataContext in such a way that changes to the UI element affect the property, and vise versa. One way to enable this is to implement the INotifyPropertyChanged interface in your DataContext. Unfortunately, this introduces a lot of boilerplate code for any property you add to the "ModelView" type. Here is how it might look in Scala:

trait IDrawable extends INotifyPropertyChanged
{    
      protected var drawOrder : Int = 0
      def DrawOrder : Int = drawOrder
      def DrawOrder_=(value : Int) {
            if(drawOrder != value) {
                  drawOrder = value
                  OnPropertyChanged("DrawOrder")
            }
      }

      protected var visible : Boolean = true
      def Visible : Boolean = visible
      def Visible_=(value: Boolean) = {
            if(visible != value) {
                  visible = value
                  OnPropertyChanged("Visible")
            }
      }
      def Mutate() : Unit = {
          if(Visible) {
              DrawOrder += 1 // Should trigger the PropertyChanged "Event" of INotifyPropertyChanged trait
          }
      }
}

For the sake of space, let's assume the INotifyPropertyChanged type is a trait that manages a list of callbacks of type (AnyRef, String) => Unit, and that OnPropertyChanged is a method that invokes all those callbacks, passing "this" as the AnyRef, and the passed-in String). This would just be an event in C#.

You can immediately see the problem: that's a ton of boilerplate code for just two properties. I've always wanted to write something like this instead:

trait IDrawable
{
      val Visible = new ObservableProperty[Boolean]('Visible, true)
      val DrawOrder = new ObservableProperty[Int]('DrawOrder, 0)
      def Mutate() : Unit = {
          if(Visible) {
              DrawOrder += 1 // Should trigger the PropertyChanged "Event" of ObservableProperty class
          }
      }
}

I know that I can easily write it like this, if ObservableProperty[T] has Value/Value_= methods (this is the method I'm using now):

trait IDrawable {
      // on a side note, is there some way to get a Symbol representing the Visible field
      // on the following line, instead of hard-coding it in the ObservableProperty 
      // constructor?
      val Visible = new ObservableProperty[Boolean]('Visible, true)
      val DrawOrder = new ObservableProperty[Int]('DrawOrder, 0)
      def Mutate() : Unit = {
          if(Visible.Value) {
              DrawOrder.Value += 1 
          }
      }
}

// given this implementation of ObservableProperty[T] in my library
// note: IEvent, Event, and EventArgs are classes in my library for
// handling lists of callbacks - they work similarly to events in C#
class PropertyChangedEventArgs(val PropertyName: Symbol) extends EventArgs("")
class ObservableProperty[T](val PropertyName: Symbol, private var value: T) {
    protected val propertyChanged = new Event[PropertyChangedEventArgs]
    def PropertyChanged: IEvent[PropertyChangedEventArgs] = propertyChanged
    def Value = value;
    def Value_=(value: T) {
        if(this.value != value) {
            this.value = value
            propertyChanged(this, new PropertyChangedEventArgs(PropertyName))
        }
    }
}

But is there any way to implement the first version using implicits or some other feature/idiom of Scala to make ObservableProperty instances function as if they were regular "properties" in scala, without needing to call the Value methods? The only other thing I can think of is something like this, which is more verbose than either of the above two versions, but is still less verbose than the original:

trait IDrawable {     
  private val visible = new ObservableProperty[Boolean]('Visible, false)
  def Visible = visible.Value
  def Visible_=(value: Boolean): Unit = { visible.Value = value }

  private val drawOrder = new ObservableProperty[Int]('DrawOrder, 0)
  def DrawOrder = drawOrder.Value
  def DrawOrder_=(value: Int): Unit = { drawOrder.Value = value }

  def Mutate() : Unit = {
    if(Visible) {
      DrawOrder += 1 
    }
  }
}