See my post here on my blog: http://gamesandtech.wordpress.com/2009/10/14/actionscript-3-specifying-events-on-interfaces/

public class MyClass { … }
public interface MyInterface extends MyClass { … }

Will not compile (which is to be expected). However, interfaces can extend other interfaces, in fact, interfaces can extend any number of interfaces.

public interface MyBaseInterface { … }
public interface MyInterface extends IEventDispatcher, MyBaseInterface { … }

So the trick to get your interfaces to have the add/remove even listener methods is rather easy. The trick is to specify which events are part of the interface contract, which is not supported by the language at the moment. Perhaps someone can come up with an approach using Filipe’s method of specifying events at the class level combining interface inheritance.

I myself enjoy the C# approach to events, in fact I wish Actionscript were C# to tell you the truth. I enjoy C# far more than I do AS3, however I enjoy the display list approach Adobe has taken in the Flash world.

I’d suggest C# event handling …

But for now, when I need an interface to define events, I do something like this:

interface ISomeLoader {
function addProgressListener(listener:Function,[whatever]):void;
function removeProgressListener(listener:Function):void;
}
class SomeLoader implements ISomeLoader {
public function addProgressListener(listener:Function,[whatever]):void{
this.addEventListener(MyEvent.PROGRESS, listener);
}
public function removeProgressListener(listener:Function):void{
this.removeEventListener(MyEvent.PROGRESS, listener);
}
}

This doesn’t define the type of event, I specify it in the comments.

Anyway this works fine for me and makes it easier to write the class clients.

event progress:ProgressEvent;

Wouldn’t you, in a similar fashion, also want to be able to declare styles, e.g.

style doingGoodProgressEffect:SomeStyleType;

But… a problem of AS abd Flex, imho, is the infiltration of so many keywords and concepts. It may be too late, but shouldn’t AS aim at simplification rather than continued keyword/concept creep?

On the other hand, is there a particular reason why AS interfaces do not support declaration of (public) vars, instead of only supporting get/set properties?

My gut feeling is that a more generic way to proceed would be to
a) adjust how events/styles (or anything currently requiring decoration via “metadata” declaration) in Flex are declared, such that they are instead declared via vars/properties of a given type
b) add support for var declaration to AS interfaces

The alternative i.e. that of adding the possibility for AS interfaces to support class/method metada decorations, might well be feasible but I suspect my hide numerous issues that may dirty the approach…

Please let me introduce you to Amethyst :-)

This is a Visual Studio Flex IDE from my company, SapphireSteel Software. It will have a full suite of Visual Studio tools for coding,, design, debugging etc. We will release two editions – a free ‘Personal Edition’ and a commercial ‘Professional’ edition. Amethyst is already available in beta and version 1.0 will be released in a few months.

Both editions have IntelliSense, code formatting/colouring/folding, debugging with drill-down etc. Amethyst Professional will also have a drag-and-drop visual designer for Flex/AIR (Flex 3 md 4) plus enhanced debugging (tracepoints, conditional breakpoints etc.) – all seamlessly integrated into Visual Studio.

More info on our web site. The blog is a good place to start: http://www.sapphiresteel.com/-Blog-

best wishes
Huw

class MyClass extends Sprite implements IMyInterface

// when using MyClass from client, cast instance as Sprite (which MyClass extends) to access built-in Sprite methods like addEventListener

var myobj:IMyInterface;
myobj = new MyClass();
Sprite(MyClass).addEventListener(…

So it could be something like

class SomeClass extends SomeBase implements ISomeInterface dispatches SomeNewFancyThing
{ … }