Event from class

programming flash
1

Hi!..
before asking question i would tell the people that i am new to OOPS… so i want to make a custom class and dispatch some events from that class…

this is custom class

package
{
import flash.display.Sprite;
import flash.events.MouseEvent;

public class SomeThing extends Sprite
{
	public function SomeThing ():void
	{
		init ();
	}
	private function init ():void
	{
		stage.addEventListener (MouseEvent.MOUSE_DOWN, doSome);
		stage.addEventListener (MouseEvent.MOUSE_UP, doSome);
		stage.addEventListener (MouseEvent.CLICK, doSome);
		stage.addEventListener (MouseEvent.DOUBLE_CLICK, doSome);
	}
	
	private function doSome(eve:MouseEvent):void
	{
		trace (eve.type);
	}
}

}

when i instantiate it like this… assuming that the class is in same directory as the .fla…

var sone:SomeThing = new SomeThing()

it gives me small error like this…

TypeError: Error #1009: Cannot access a property or method of a null object reference.
at com.drmax.ui::SomeThing/init()
at com.drmax.ui::SomeThing()
at Untitled_fla::MainTimeline/frame1()

can some one tell me why its happening and how can i add events on stage from a class…