when does the stage become initialised?

Question

I have a singleton class that inherits from sprite so that it can access the stage, like this..

package  
{
    import flash.display.Sprite;

    public class C extends Sprite
    { 
     private var _grid:Array = new Array();

     public function get Grid():Array
     {
      return _grid;
     }  

     private static var _instance:C;

     public static function get Instance():C
     {
      if (_instance == null)
      {
       _instance = new C();
      }

      return _instance;
     }

     function C() 
     {
      this.InitGrid();
     }

     private function InitGrid():void 
     {
      var gridWidth:Number = stage.width / 10;
     }
    }
}

This throws the error

TypeError: Error #1009: Cannot access a property or method of a null object reference.
    at C/InitGrid()
    at C()
    at C$/get Instance()
    at C()
    at Main()

If I replace stage.width with an int the code executes OK. is this because the object has not been added to the displayList of any children of the stage?

Thanks

Answer 1

Yes. The Sprite will only have a stage property once it's a part of the Display list.
To get the stage you will need to either give your singleton a reference to the stage or add it to the Display list. If you choose the latter you can add a listener Event.ADDED_TO_STAGE, and handle that accordingly inside your singleton.