432 | Chapter 12: Model-View-Controller Pattern
addEventListener(type:String,
listener:Function,
useCapture:Boolean = false,
priority:int = 0,
useWeakReference:Boolean = false):voidremoveEventListener(type:String,
listener:Function,
useCapture:Boolean = false):voiddispatchEvent(event:Event):BooleanFor the model to serve as a concrete subject in an observer pattern, it needs to imple-
ment theIEventDispatcherinterface. However, the easiest way for a user-defined
class to gain event dispatching capabilities is to extend theEventDispatcher class.
Observers register listener methods to receive event notifications from
EventDispatcher objects through theaddEventListener( ) method.
The model
Our model holds the character code of the last key pressed in a property. It needs to
implementsetterandgettermethods to enable the view and controller to access and
modify it. Let’s first define an interface for our model (Example 12-1).
TheIModelinterface shown in Example 12-1 extends theIEventDispatcherinterface
and defines two methods to get and set the character code of the last key pressed.
Because theIModelinterface extendsIEventDispatcher, any class implementing it has
to implement all the methods defined in both interfaces. TheModelclass shown in
Example 12-2 implements theIModel interface.
Example 12-1. IModel.as
package
{
import flash.events.*;
public interface IModel extends IEventDispatcher
{
function setKey(key:uint):void
function getKey( ):uint
}
}
Example 12-2. Model.as
package
{
import flash.events.*;
public class Model extends EventDispatcher implements IModel
{