I effectively gave up Flash when I came to Public and it’s now a whole year since I did any significant Flash work. In this short time AS3 has really come of age, there are tonnes of serious libraries, from fractals to physics, and PaperVision 3D seems almost omnipresent. The prospect of going back to the ActionScript freelance circuit after a year on the wagon would be quite daunting.

The reasons I’ve done little Flash since I’ve been at Public are perfectly sound: I work with two brilliant Flash developers who make up 50% of our development team, and rather than everyone doing a bit of everything, we all specialize quite specifically. I cover all the back end work, and do a lot of server admin; so ActionScript in my personal world is now just a fond legacy of my freelance career.

ActionScript is still of great interest to me – JASPA is closely modelled on AS3, and at Public Flash makes up the majority of our projects, so I obviously stay up to date on its progress. But I’ve spent so many hours writing ActionScript that it seems a shame I won’t be so directly involved in its future. I started using Flash in version 3 and so I’ve seen ActionScript develop from nothing in real time. I remember when Flash 5 came out and we could finally write real code. I made a concious decision there and then to ditch Lingo, because it was starting to become obvious that Flash had a brighter future on the web. This turned out to be a very good decision.

As usual with my blog posts I feel I need to write some kind of conclusion (recalls GCSE English lessons), but I don’t have one; except I miss Flash, it’s awesome. The end.

Unlike JavaScript and AS2, AS3 supports method closures implicitly; so I made sure they were built into the JAS language. Such a thing is not native to JavaScript so the JASPA compiler automatically generates a call to helper function jaspa.closure whenever an object’s method is referenced.

If you’ve ever used Delegate.create in AS2, then you’ve encountered this issue. If you don’t see the problem, consider this example in JavaScript:

1. var Cat = function(){
2.      this.voice = ‘Miaow’;
3. }
4. Cat.prototype.speak = function(){
5.      alert( this.voice );
6. }
7.  
8. var Sammy = new Cat;
9. Sammy.speak(); // alerts “Miaow”
10.  
11. var Callback = Sammy.speak;
12. Callback(); // alerts undefined

As soon as we’ve created a reference to the function member, we’ve severed it from its owner, so when we call it, it’s not being called on the object. In JavaScript and AS2 we need to use a method like Delegate.create to explicitly create a closure. Here’s an example:

1. function makeClosure( obj, func ){
2.      var closure = function(){
3.          return func.apply( obj, arguments );
4.      }
5.      closure.apply = function( obj, args ){
6.          return func.apply( obj, args );
7.      }
8.      closure.call = function( obj ){
9.             var args = [];
10.              for( var i = 1; i < arguments.length; i++ ){
11.                  args.push( arguments[i] );
12.              }
13.             return func.apply( obj, args );
14.      }
15.      return closure;
16. }

It’s basically a wrapper function which seals in the original arguments. Additionally apply and call must be overridden or calling them directly will spoil the party. Try it with the Cat example and you’ll see the desired result.

1. var Callback = makeClosure( Sammy, Sammy.speak );
2. Callback(); // alerts “Miaow”