Type Coercion error when casting an object loaded in a different application domain

My application currently contains a number of Widgets that are managed by a Widget Manager. When the user clicks on a widget (e.g. a Helper widget), the Widget Manager loads the widget into a separate sibling application domain with the following line of code:

wgtInfo.load(null, null, null, moduleFactory); //wgtInfo = IModuleInfo

However, I am unable to use the widget's variables and functions later on. I attempt to find the Helper widget from the Widget Manager's list of widgets, and I do successfully. But when I try to caste the Helper Widget from type IBaseWidget (the interface all widgets share) to type HelperWidget, I receive the following error:

TypeError: Error #1034: Type Coercion failed.....

This is because the application domain of the class trying to use the Helper widget is different from the application domain of the Helper Widget. I tried to fix this by loading all widgets into the same application domain as the loader:

wgtInfo.load(ApplicationDomain.currentDomain, null, null, mo开发者_StackOverflow中文版duleFactory);

I now get the following error whenever I attempt to load the Helper widget:

TypeError: Error #1009: Cannot access a property or method of a null object reference.

How can I load my Helper widget into a common application domain that is accessible by the other widgets?

I believe your problem comes from the class not being included in the swf. This is because Flash doesn't compile in classes in a swf if they aren't used to reduce filesize. To prevent this, you only need to create a variable with the helper class you need in that class, like this:

private var helper:HelperWidget;

See if that helps.

I'm gonna repost my 'comment' as a real answer. I'm guessing that the error is not based on the ApplicationDomain but based on which classes you are being compiled into your Module. When Flex compiles the SWF it automatically optimizes unused classes out of the SWF. You can force them back into the SWF in one of two ways:

1. Use the compiler argument include-libraries to force the Flex compiler to add the class to your SWF.

2. Add a fake variable in in your application so that the Flex compiler thinks it is used and adds it to the final SWF. Something like this.

   private var myFakeObject : HelperWidth;

After trying a number of solutions unsuccessfully (including the other responses on this page), I resorted to another, event-driven, solution.

I ended up dispatching a custom event to notify my other widgets when the Helper widget had completed loading:

(HelperWidget.mxml)

ViewerContainer.addEventListener(AppEvent.WIDGET_OPEN_TAB, widgetOpenTabHandler); //listen for other widgets to open a tab within the Helper Widget
ViewerContainer.dispatchEvent(new AppEvent(AppEvent.WIDGET_READY_OPEN_TAB)); //notify other widgets that loading is complete

My other widgets listen for this event to fire, and upon completion, dispatch another event (AppEvent.WIDGET_OPEN_TAB) to perform a function within the Helper widget.