Inheritance problem: base class does not see stage instances

Question

I'm writing a series of Search windows for an application. I create the FLA files on the stage, each has 3 simple buttons: next_btn, prev_btn, and close_btn. Those all have event listeners which call findNext(), findPrev() and closeWin() respectively. Each search window looks for different things, some with a text box and some with a combo, etc.
So I have a base class com.search that extends Sprite and adds the eventListeners at startup (actually, on addedToStage). Like this:
function isAddedToStage(evt:Event){
   next_btn.addEventListener("click",findNext);
   prev_btn.addEventListener("click",findPrev);
   close_btn.addEventListener("click",closeWin);
Then I write the appropriate find functions in each derived class.
For example, I have
package com {
     import com.search;
     class searchText extends search {
In my FLA file, I set the class to com.searchText.
But when I compile and run the window, I get runtime errors:
ReferenceError: Error #1065: Variable next_btn is not defined.
at com::search()
at com::searchtext()
If I add the event listeners in the derived class rather than the base, it works fine. But that seems to defeat the purpose of inheritance, plus it infers that I won't be able to derive new classes/swfs from those derived classes.
So the question is, how does one reference objects created on the stage from a base class of that document's class?

Answer 1

Found it. After messing around with trying dynamic classes and overriden functions that returned the desired button (that worked, but was ugly.)
Simply and silly once you know how.
You have to explicitly reference the stage objects (or any newly declared methods or properties) in the derived class as members of "this" in the base class - so:
class Search {
function isAddedToStage(evt:Event){
   this.next_btn.addEventListener("click",this.findNext);
   this.prev_btn.addEventListener("click",this.findPrev);
   this.close_btn.addEventListener("click",closeWin);
function closeWin(e:Event){
and then create the buttons on stage in the FLA using the derived class.
You can also declare the event handling functions in the base class as empty functions and then override them in the derived classes. Or fill in the functions in the base class to throw a runtime error, and then override - that's as close to an abstract class as you can get, I think.