How can I invoke functions declared in my DocumentClass, Please?

Question

Hello Everyone,
I have been at it for days now and don't know how to get this going. I have DocumentClass and I have a simple function which returns stage width. I now would like to call this function from othr class which exist within the same package as my DocumentClass. I am able to trace the stage width when I invoke stageWidth() function from the DocumentClass. As I to understand, if the function is public, and it is being accessed by a class that exist within the same package, I should be able to access the function withou any issues. And If I declare the function as STATIC then it is global and can be accessed by classes from other packages. Can anyone help me understand what am I doing wrong, please.
Function that I have written:
public function stageWidth()
   return stage.stageWidth;
I am calling this function from Background class by class reference like this:
DocumentClass.sWidth();
I get this error:
1180: Call to a possibly undefined method sWidth.
Appreciate all your help. Thank you.

Answer 1

In addition to my previous replies.
Why do you need to access stage parameters via calling DocumentClass method? Stage is accessible by all the objects placed on it. So, in your Background class you can read stage.stageWidth directly. Again, this is given that the instance of Background is added to stage.
Also, your Background class must extend some DisplayObject because, obviously, it will become an object to be displayed. Most often it is Sprite. In the code example below I added listeners for both when Background instance is added to stage and when it is added to display list. Observing the sequence may be very educational.
So you class Background shoul look like this:
package com.as3.learning {
    import flash.events.*;
    import flash.display.*;
    import flash.text.*;
    public class Background extends Sprite
        public function Background()
            trace(this + " constructor");
            // listen to when it is added to display list
            addEventListener(Event.ADDED, onAddedToList);
            // listen to when it is added to stage
            if (stage) init();
            else addEventListener(Event.ADDED_TO_STAGE, init);
        // this method can be called in two cases:
        // 1. when the instance is placed on stage and
        // 2. before it is placed.
        public function init(e:Event = null):void
            removeEventListener(Event.ADDED_TO_STAGE, init);
            // only now stage is available
            trace(this + ".init: stage.stageWidth: " + stage.stageWidth);
            trace(this + ".init: DocumentClass.sWidth() = " + DocumentClass.sWidth());
        private function onAddedToList(e:Event):void
            trace(this + ".onAddedToList: stage.stageWidth: " + stage.stageWidth);
            trace(this + ".onAddedToList: DocumentClass.sWidth() = " + DocumentClass.sWidth());