I'm building a video player using Flash CS4 (hereby referred to as "Flash") to create the graphic symbols and compiling and debugging with Flash Builder 4 ("FB4"). Here are the steps I take in my current workflow: --Create the graphic symbols in Flash. I've created a few different symbols for the player, but I'll focus on just the play/pause button ("ppbutton") here. --In the Library panel, I go to the ppbutton symbol's Linkage properties and link to a class named assets.PlayPauseButtonAsset that extends MovieClip. I do not actually have an assets package nor do I have a class file for PlayPauseButtonAsset as Flash will create them for me when I publish. --In Flash's Publish settings, I set the project to export a SWC that will be used in FB4, called VideoPlayerAssets.swc. --After the SWC is created, I create my FB4 project called "VideoPlayer" and add the SWC to my path. FB4 creates the class VideoPlayer in the default package automatically. --In VideoPlayer.as, I import assets.*, which imports all of the symbol classes I created in Flash and are available via VideoPlayerAssets.swc. I can now instantiate the ppbutton and add to the stage, like this: var ppbutton:PlayPauseButtonAsset = new PlayPauseButtonAsset(); addChild(ppbutton); At this point ppbutton doesn't have any functionality because I didn't create any code for it. So I create a new class called video.controls.PlayPauseButtonLogic which extends assets.PlayPauseButtonAsset. I add some logic, and now I can use that new class to put a working ppbutton on the stage: var ppbutton:PlayPauseButtonLogic = new PlayPauseButtonLogic(); addChild(ppbutton); This works fine, but you may be asking why I didn't just link the ppbutton symbol in Flash to the video.controls.PlayPauseButtonLogic class in the first place. The reason is that I have a designer creating the UI in Flash and I don't want to have to re-publish the SWC from Flash every time I make a change in the logic. Basically, I want my designer to be able to make a symbol in Flash, link that symbol to a logically named class in Linkage properties, and export the SWC. I do not want to have to touch that .fla file again unless the designer makes changes to the symbols or layout. I'm using a versioning system for the project as well and it's cleaner to make sure only the designer is touching the .fla file. So, finally, here's the issue I'm running into: --As the design gets more complex, the designer is nesting symbols to position the video controls on the control bar. He creates a controlbar symbol and links it to assets.ControlBarAsset. The controlbar symbol contains the ppbutton symbol. --The designer publishes the SWC and ControlBarAsset is now available in FB4. I create new class called video.controls.ControlBarLogic that extends assets.ControlBarAsset so I can add some logic to the controlbar, and I add the controlbar to the stage: var controlbar:ControlBarLogic = new ControlBarLogic(); addChild(controlbar); --This works, but the ppbutton doesn't do anything. That's because ppbutton, while inside controlbar, is still only linked to PlayPauseButtonAsset, which doesn't have any logic. I'm no longer instantiating a ppbutton object because it's part of controlbar. That's where I'm stuck today. I can't seem to simply re-cast controlbar's ppbutton as PlayPauseButtonLogic as I get a Type error. And I don't want to have to make a class that has to instantiate each of the video player controls, the place them at their x and y values on the stage according to how the designer placed them, as that would require me to open the .fla and check the various properties of a symbol, then add those values to the code. If the designer made a change, I'd have to go into the code each time just to update those properties each time. Not good. How do I re-cast nested symbols to use the logic classes that I create that extend the asset classes? Remember, the solution is not to link Flash symbols to actual classes so I don't have to keep recompiling the SWC, unless there's a way to do that without having to re-compile the SWC. I want the designer to do his thing, publish the SWC, and be done with it. Then I can take his SWC, apply my logic to his assets, and be able to debug and compile the final SWF.