title: AS3: How can I fire events when a property is changed in a über class?
body: <p>I have a TextField inside a Sprite and I always want the alpha of the TextField to be equal to the alpha of the sprite. How can i subscribe to the changes made in the Sprite? I guess i need to fire a PropertychangeEvent some how, but I can't see that sprite supports this out of the box?</p>
  
  <pre><code>class TextWidget extends Sprite{  
    private var textfield:TextField;    
    public function TextWidget(){  
      textfield = new TextField();  
      textfield.alpha = this.alpha;  //does'n help  
      addChild(textField);  
  ??  
    this.addEventListener(PropertyChangeEvent.PROPERTY_CHANGE, updateAlpha);  
  ??  
    }
    private function updateAlpha(event:PropertychangeEvent):void{  
      textfield.alpha = this.alpha;  
    }  
  }  
  </code></pre>