Module warning in Flex4 migration - apache-flex

Question

I'm migrating from flex 3.5 to flex 4.6 with flex 3 compatibility mode. I got this warning in my two modules:
Module1 is a module or application that is directly referenced. This will cause Module1 and all of its dependencies to be linked in with index. Using an interface is the recommended practice to avoid this.
I have module1.mxml and module1controller.as with several functions, then this module is loaded in many applications files using mx:ModuleLoader. Like i said this is a compatibly mode so I'm not sure if i can use spark on this.
I think i don't understand what this warning means, everything works in the application. Can someone give me an example of a Interface that can fix this problem.

Answer 1

Here is the example.
You want your module to do some things for your main app. For example, let your module provide some user notifying functionality.
So, we declare interface for that functionality:
package test
{
public interface IAlertable
{
function alert(message:String):void;
}
}
Then we declare that our module can provide functionality, declared in that interface:
<?xml version="1.0" encoding="utf-8"?>
<mx:Module xmlns:fx="http://ns.adobe.com/mxml/2009"
xmlns:s="library://ns.adobe.com/flex/spark"
xmlns:mx="library://ns.adobe.com/flex/mx" layout="absolute" width="400" height="300"
implements="test.IAlertable"
>
<fx:Script>
<![CDATA[
import mx.controls.Alert;
public function alert(message:String):void{
Alert.show(message,message);
}
]]>
</fx:Script>
</mx:Module>
And then in main application we shall never be interested in our module class name or implementation, we just need to know that it has functionality we desire from it:
<fx:Script>
<![CDATA[
import test.IAlertable;
protected function handleCreationComplete():void
{
moduleLoader.loadModule('test/TestModule.swf');
}
protected function testInterface():void{
var alertModule:IAlertable = IAlertable(moduleLoader.child);
alertModule.alert('Hello module world!');
}
]]>
</fx:Script>
<mx:ModuleLoader id="moduleLoader" width="100%" height="100%" ready="testInterface()"/>
Now you can change implementation of your functionality at any time without recompiling main app(in current example, you can do trace instead of alert), you can even create different module class with that interface, and main app will never notice the change.