AMF is crucial for all types of serialization and communications. All native data serialization is customarily handled by the class ByteArray. When serialized, the data type information is marked out by the name included in the metadata tag RemoteClass.

Example 6-1 is a small example from the Flash Builder’s NetworkingSamples project that comes with the book. It includes an application RegisteredClassvsUnregistered.mxml and two classes: RegisteredClass and Unregistered.

package
{
    [RemoteClass(alias="com.RegisteredClass")]
   public class RegisteredClass{
   }
}

package
{
   public class UnregisteredClass{
   }
}


<?xml version="1.0" encoding="utf-8"?>
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml"
                                    creationComplete="test()">
<mx:Script>
   <![CDATA[
      import flash.utils.ByteArray

      private function serializeDeserialize(a:Object) : void {
         var ba : ByteArray = new ByteArray();
         ba.writeObject(a);
         ba.position = 0;
         var aa:Object = ba.readObject();
         trace( aa );
      }

      private function test():void {
         serializeDeserialize( new RegisteredClass());
         serializeDeserialize( new UnregisteredClass());
      }
   ]]>
</mx:Script>
</mx:Application>

In Example 6-1, the function serializeDeserialize() serializes the object passed as an argument into a ByteArray, and then reads it back into a variable aa of type Object. The application makes two calls to this function. During the first call, it passes an object that contains the metadata tag, marking the object with a data type RegisteredClass; the second call passes the object that does not use this metadata tag. Running this program through a debugger displays the following output in the console:

[SWF] /NetworkingSamples/NetworkingSamples.swf -
                                    798,429 bytes after decompression
[object RegisteredClass]
[object Object]

Annotating a class with the RemoteClass metadata tag allows Flash Player to store, send, and restore information in the predictable, strongly typed format. If you need to persist this class, say in AIR disconnected mode, or communicate with another .swf locally via the class LocalConnection, following the rules of AMF communications is crucial. In the example, RemoteClass ensures that during serialization, the information about the class will be preserved.