[flexcoders] Returning 'this' from an overridden method?

[David_Stafford]

Please pardon this simple-minded question from an AS3 novice.

My base class often returns 'this' from methods which makes it 
convenient to write code like:

  camera.move( 10, 12 ).rotateX( 45 ).rotateY( 90 );

The problem comes when code extends the base class and overrides one 
of these functions.  The compiler insists, correctly, that the return 
type of an overriding function must match the one in the base class.  
What I want to do is return the 'this' object that is of the type of 
the derived class.  Is this possible?

The following is a contrived example to demonstrate.  It won't 
compile because the overridden function in the derived class wants to 
return a type of MyCamera rather than Camera:


public class Camera
  {
  var x:int = 0;
  var y:int = 0;

  public function move( x:int, y:int ) :Camera
    {
    this.x += x;
    this.y += y;

    return( this );
    }  
  }

public class MyCamera extends Camera
  {
  override public function move( x:int, y:int ) :MyCamera
    {
    super.move( x, y ); 

    if( x < 0 )  x = 0;
    if( y < 0 )  y = 0;

    return( this );
    } 
  }