Flex watch bindable property other class

Question

I'm creating an application using Flex 4. When the app is started, it reads a XML file and populate objects. The .send() call is asynchronous, so I would want to listen/watch to this populated object, and when it has finished, dispatch an event for other classes, so they can use it.

package model{
    public class LectureService extends HTTPService{
        [Bindable]
        private var _lecture:Lecture;

        ...
}

The xml is parsed correctly and loaded inside the object lecture of the class Lecture.

If I use the MXML notation in the main.mxml app, it works fine (the object is used when the it is populated after the async request):

<mx:Image id="currentSlide" source={lectureService.lecture.slides.getItemAt(0).path} />

BUT, I have another ActionScript class and I'm not able to listen to this dispatched (by [Bindable]) event.

package components{

    public class LectureSlideDisplay extends Image
    {       
        public function LectureSlideDisplay()
        {
            super();

            this.addEventListener(PropertyChangeEvent.PROPERTY_CHANGE, onChangeTest);
        }

        private function onChangeTest(e:PropertyChangeEvent):void {
            trace('test');
        }

I have already tried:

1. using (like above) addEventListener(PropertyChangeEvent.PROPERTY_CHANGE, methodName).
2. tried to change the [Bindable] to [Bindalbe("nameEvent")] and listen for this, nothing.
3. using CreateWatcher method, doesn't work.

4. tried to have a look to the generated code of the class, but didn't help me

   if (this.hasEventListener("propertyChange")){ this.dispatchEvent(mx.events.PropertyChangeEvent.createUpdateEvent(this, "lecture", oldValue, value)); }

How can I listen and have the populated object in another class? Maybe the problem is that I'm listening from another class, but in this case how can I implement this? It seems the event is dispatched, but I can't listen to it.

Answer 1

Consider to use BindingUtils class. You can found documentation here. And a couple of usage samples: one, two.

Answer 2

You can't solve all your problems by just extending the class. You should really look into Commands for your HTTP requests.

The change property event is used internally for watchers and won't dispatch in the overall component. What you want to do for your LectureSlideDisplay is to override the source setter. Every time it is called, a new value is being binded to it:

package components{

    public class LectureSlideDisplay extends Image
    {      
        override public function set source(value:Object):void
        {
           super.source = value;
           // do whatever
        } 

        public function LectureSlideDisplay()
        {
            super();
        }
   }
}

You should really read up on how Binding works.

Answer 3

For who wants the answer, I have resolved changing the addEventListener object. It is not right to use:

this.addEventListener(...)

Use instead:

lectureService.addEventListener(...)

I have changed my code to listen to this event in the main app MXML, and then inside the handler method, call the public method of your components to use the new data.