Gigs - Easier ActionScript Event Handling

Some time ago I created Protection. It was a library intended to help me write more readable ActionScript code without breaking out of the paradigms that were set out by Adobe. You can find a more thorough explanation and motivation in an article I wrote earlier this year. I have been using it a lot now and as much as I like the basic idea, I came to realise that I had made a few wrong decisions. Most importantly:

  • overcomplicated nomenclature: in a silly attempt at originality I used military metaphors throughout the library (Sentries, Captains, Spies, etc.). These names make the code actually less transparent to someone who doesn’t know where they originated (i.e. anyone but me). This is in clear violation with my original intent: more readable code.
  • too many optional arguments: a lot of different configuration was passed through one method with a bunch of optional arguments. Again, this would not be transparent to someone who read such code for the first time.
  • used inheritance (instead of composition) to add the functionality to custom components
  • string-based conditionals: "r:propertyA", "f:propertyB" to pass ‘propertyA’ to the result handler and ‘propertyB’ to the failure handler? Not so pretty.

Enter Gigs (a.k.a RIAstar events)

So I decided to rethink the whole thing. To start with, the library name will remain my only attempt at originality. But let’s get down to the real stuff. This is how you use Gigs for tracking native Events:

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follow(submitButton).by(MouseEvent.CLICK).handle(submit);

private function submit():void {
    //do some submitting
}

You can also join a ‘gigs.properties’ file to the application in which you can associate default event types to specific classes. For instance 95% of the time on Buttons we listen for CLICK events. So we register a default for that:

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spark.components.supportClasses.ButtonBase = click

And then we can write the following to do the same thing as before:

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follow(submitButton).handle(submit);
//we can still explicitely listen for
//another event than the registered default
follow(submitButton).by(MouseEvent.MOUSE_DOWN).handle(startDrag);

Passing property values

The ‘handle’ method takes one additional …rest argument to which you can pass all the event properties you want pass to the result handler. For example (I’ve registered the ListBase class with the IndexChangeEvent.CHANGE event type):

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follow(itemList).handle(editItemAt, "newIndex");

private function editItemAt(index:int):void {
     //open item editor
}

Unfollowing (a.k.a. removing event listeners)

There are three ways to stop following Events.

Very specifically:

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unfollow(submitButton).by(MouseEvent.CLICK).handle(submit);

Somewhat specifically (this will remove all event handlers that react to a CLICK event):

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unfollow(submitButton).by(MouseEvent.CLICK).all();

Loose cannon (removes all event listeners for all event types for the given IEventDispatcher):

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unfollow(submitButton).all();

To be continued

That’s it for now. I have yet to recreate all functionality that existed in Protection, but I will hopefully get to that soon.

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