[AS3] Programming Actionscript 3.0

Last edited by Codemonkey : 2006-07-08 at 15:37.
























I've been studying the huge 514 pages pdf Programming Actionscript 3.0 guide this Saturday midday. I've done 300 pages and the rest is about the new libraries mainly, how to communicate, parse xml, draw vectors and what not, so I'll save that for another time when I can move my eyes again. Oh btw, on page 160, the diagram shows Loader, Sprite and Stage as subclasses of SimpleButton, which should be DisplayObjectContainer as indicated in the text below the diagram.

So even though AS3 has some very exciting new features and improvements, there are a couple of things I don't like as much. I was wondering what your opinions are.

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For example AS3 adds the variable arguments option, which is a parameter defined as "..." to indicate a dynamic number of arguments. You would only need this if you compile AS3 in strict mode, where the passed arguments must match the defined number of parameters. If you would like a dynamic number of arguments in strict mode compiling, you would define a parameter with "..." meaning "rest":


ActionScript Code:
function traceArgArray(x: int, ... args) {for (var i:uint = 0; i < args.length; i++) {trace (args[i]);}}traceArgArray(1, 2, 3);// output:// 2// 3  
Now what I don't like about this is that it hides the 'arguments' property of the function, because according to the programming guide, the ... (rest) argument just completely negates it.





Programming Actionscript 3.0 p102
[...] Use of this parameter makes the arguments object unavailable. Although the ... (rest) parameter gives you the same functionality as the arguments array and arguments.length property, it does not provide functionality similar to that provided by arguments.callee. You should ensure that you do not need to use arguments.callee before using the ... (rest) parameter.

Why I don't like it? Because in a number of situations I would like to be able to reference the function I'm currently in using arguments.callee to recall a variable for example I put there before. Or, because I defined the function as anonymous (passed as reference or something), which is recursive (needs to call itself by using arguments.callee()).

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Something else I don't really like is that you can have statements outside functions within a class definition. For example, this is valid:


ActionScript Code:
function hello() : String {trace ("hola"); }class SampleClass {hello();trace("class created");}// output when class is createdholaclass created
I don't like this very much because it encourages use of globals, which you should try to avoid as much as you can (it counters encapsulation and cohesion). Also, having code all over the place like this makes it difficult code to read.

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The last thing I noticed that I'm not sure I like is that you can't have private constructors anymore. They can only be public. So there's no way to design a class with responsibility of creating or managing its own instances from static methods. No more Singleton pattern (although it's been considered an anti-pattern as well). It's always a dubious issue whether a class should be so statically equipped with responsibilities, but at least I'd like to have that option...

So ehh anyway, that's what I thought off so far. To finish off with some good notes, it's cool that you can now define default values for parameters in a function.


ActionScript Code:
function defaultValues(x:int, y:int = 3, z:int = 5) {trace (x, y, z);}

I think I really like the new way of handling XML in AS3. The new XML handling in AS3 a blend of XPath and conventional XML access (by means of array accessors and dot syntax). Which results in notations like var employee = x.employee.(@id == 347);

At first I thought that it was pretty ugly actually, to suddenly mix some weird notation in the dot-syntax, like "xml.@quantity", but this works a lot more intuitive for non-hardcore coders. I mean, just look at it:


ActionScript Code:
var total:Number = 0;for each (var prop:XML in myXML.item) {total += prop.@quantity * prop.price;}
And also ofcourse you can now print an XML object to string in a formatted way with nice indentation.

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