Error with scope

programming flash
1

I have a Hero class and am trying to move the mc character:

class Hero {
     private var hero:MovieClip;

     function Hero() {
          hero = _root.attachMovie("hero", "hero", _root.getNextHighestDepth());
          hero.onEnterFrame = mover;
     }

     function mover() {
          this._x += 5;
     }
}

This throws the following error:

There is no property with the name '_x'.
     		this._x += 5;

Total ActionScript Errors: 1 	 Reported Errors: 1

I tried changing hero.onEnterFrame = mover to hero.onEnterFrame = mover.call(hero); but that doesn’t work either.

This does work but it’s not how I would like to have structured the code:

hero.onEnterFrame = function() { this._x += 5 }

Any ideas?