Structural Types in Scala 2.6.0-RC1

An interesting feature that comes with Scala 2.6.0-RC1 is Structural Types.

This feature allows you to specify a type by specifying characteristics of the desired type. For example the following function take objects that have a setText method:

   def setElementText(element : {def setText(text : String)},
                      text : String) = {
       
       element.setText(text.trim()
                           .replaceAll("\n","")
                           .replaceAll("\t","   "))
   }

This method can be called with any object that have a setText method. For example:

      val display = new Display()
      val shell = new Shell(display)
      
      val c = new Composite(shell,SWT.NONE)
      val layout = new GridLayout
      layout.marginTop = 10
      layout.marginLeft = 10
      layout.numColumns = 2      
      c.setLayout(layout)
      val label = new Label(c,SWT.NONE)
      val textControl = new Text(c,SWT.NONE)

      setElementText(label,"   Hello\tWorld  ")
      setElementText(shell,"The title  ")
      setElementText(textControl,"Text goes here\n")

Here setElementText is called with instances of Shell, Text and Label which don't share a common super class that have a setText method.