title: actionscript 3.0 referencing a custom class of a main swf from a loaded swf's custom class
body: <p>I am writing educational software that utilizes a single "application" swf, which loads external "topic" swf files (containing library items specific to the topic).  Each of these external "topic" swf files also utilizes custom classes that solve calculations specific to the topic (ex. trigonometry class for the trigonometry.swf topic file).</p>
  
  <p>I want the trigonometry class of the trigonometry.swf to be able to reference a custom class method that exists in the main "application" swf.  If it helps to know the context, I want the user working on trigonometry to be able to type in the trig function the believe to be correct (sin, cos, or tan) and "check" to see if they are right.  The "indicate_right_wrong" method exists in a "grader" custom class of the main "application" swf (so that any changes I make to this class will be updated throughout all topics).  So...how do I reference a custom class method of a main swf FROM an externally loaded swf file's own custom class?  </p>
  
  <p>I DO have the result working when I import the "grader" custom class into each "topic" swf and reference it directly, but I don't want to have to re-publish each topic swf if I make a change to the "grader" custom class.  Thus, I'm trying to have each topic capable of referencing the "grader" custom class when it exists within the main "application" swf.</p>
  
  <p>The error I get when I try using variations of parent or parent.parent are <code>property grader_class not found on flash.display.Stage</code> (for parent) and <code>Cannot access a property or method of a null object reference.</code> (when using parent.parent).</p>
  
  <p>Thank you for any help you can provide.</p>