title: Custom AS3 class is null after being added to Array
body: <p>I'm a C# developer who is trying to learn some AS3, so this is going to be a pretty newbie question.</p>
  
  <p>I'm getting confused with regards to scope and GC, as I have a custom MovieClip-extending class (Slide) which I create instances of within a loop and push() into an Array, but afterwards the items are null when I pull them out of the collection.</p>
  
  <pre><code>var ldr:URLLoader = new URLLoader();
  ldr.load(new URLRequest("presentation.xml"));
  ldr.addEventListener(
      Event.COMPLETE,
       function(e:Event):void {
           config = new XML(e.target.data);
           for (var i:Number = 0; i &lt; config.slides.slide.length(); i++)
           {
               var node = config.slides.slide[i];
               var slide:Slide = new Slide();                      
               slides.push(slide);
  
               addChild(slide); // Works fine
           }
       }
  );
  
  slides.forEach(function(e:*, index:int, array:Array):void
      {
          addChild(e); // Causes "Parameter child must be non-null" exception
      }
  );
  </code></pre>
  
  <p>I would like to be able to references the slides later in order to toggle them as needed - how can I keep the reference to my new objects?</p>
  
  <p><strong>Update:</strong> It appears there were two problems with this.  The forEach call was being made before the URLLoader's complete event was called, and also forEach doesn't seem to work as expected.  Here is the final working code:</p>
  
  <pre><code>var ldr:URLLoader = new URLLoader();
  ldr.load(new URLRequest("presentation.xml"));
  ldr.addEventListener(
      Event.COMPLETE,
      function(e:Event):void {
          config = new XML(e.target.data);
          for (var i:Number = 0; i &lt; config.slides.slide.length(); i++)
          {
              var node = config.slides.slide[i];
              var slide:Slide = new Slide();                      
              slides.push(slide);
          }
          for each (var sl in slides)
          {
              addChild(sl);
          }
      }
  );
  </code></pre>