Pass the parent class reference to son class

programming flash
1

Hi to everybody,
How can pass the parent class reference to a son class???


public class Game extends MovieClip{
    public var cards : MyCards;

    public function Game(){
        trace("this: " + this);  //  this: [global object]
        cards = new MyCards( this );
    }
}



public class MyCards extends MovieClip{
    public var ref : MovieClip;

    public function MyCards( ref : MovieClip ){
        trace("ref: " + ref);  // ERROR
    }
}

The Error is:
[COLOR=#ff0000]TypeError: Error #1034: Type Coercion failed: cannot convert global@38fef601 to flash.display.MovieClip.[/COLOR]