Inheritance constructor question

1

what is the correct method for a constructor in a base class and a child class?

for instance i have a class called “Planet” and a subclass “Terran”
it will run fine until i uncomment the “extends planet”

the reason i want it to extend the Planet class is that i want to have functions in all the “Planet Type” classes that are overriding the initial definition in the Planet class, much like virtual functions and abstract base classes in C++

planet code


public class Planet extends Sprite
{
        public function Planet ( planetType:uint, posX:Number, posY:Number ):void
        {
            if ( planetType == 0 )
            {
                var terran:terran_mc = new terran_mc();
                terran.x = posX;
                terran.y = posY;
                addChild ( terran );

                var blah = new Terran();
                blah.drawTerran();
            }
        }

}

terran code

internal class Terran //extends Planet
{
        public function drawTerran():void
        {
            trace("Drawing a terran planet");
        }
}