mx:Module and Unsupported Spark Components
Written by Simon Bailey
Just to note a minor gotcha to be aware of when using mx:Module’s with Flex 4. Certain Spark components are not supported within mx:Module, two of which are: + s:layout + s:states
A suggested workaround for this is to either add a view component which extends a Spark component such as s:Group to your mx:Module, or simply nest all components in the mx:Module within an e.g. s:Group.
If your aware of exactly what is not supported in mx:Module’s in a Flex 4 project, or other unsupported/problematic aspects for that matter please report on http://bugs.adobe.com/jira (and if you would list [module related] them as a comment below) so other devs are not left wasting time on why certain code is not working?