After all the excitement since the annoucement, Flash MX 2004 and Studio MX 2004 are available for download (fully functional 30-day trials) and purchase!
Also available are Flash Player 7 and Flash Remoting Components for Flash MX 2004.
Back in the good old days of Flash 5 and MX, trying to do inheritance in ActionScript required some knowledge of what goes on behind the scene. Also, the infamous superclass invocation bug haunted developers for almost three years.
Now in ActionScript 2.0, with the new OOP-specific keywords, inheritance is much simpler:
class Parent {
}
class Child extends Parent {
}That’s all. And the keyword “super()” in the Child class constructor is not even mandatory because the compiler inserts it for you!
As for the superclass invocation bug, it is now fix for Flash player 7!
In Flash MX 2004, some of the component code hints are not listed in AsCodeHints.xml or UIComponents.xml. As a result, what used to be a common thing to do in MX by using code hints such as _cb for ComboBox, does not work now.
Well, there are two solutions:
1) Add you own code hints information to the two files mentioned above.
2) Reference the component class in your code:
var sp:mx.containers.ScrollPane;
Now when you type sp. the list of ScrollPane methods and property is displayed!
Thanks go to Rebecca Sun of Macromedia for this tip.
Here are some of the new features in ActionScript 2.0, and why one would want to use it instead of ActionScript 1.0 (yes, you can still use the older syntax in Flash MX 2004).
ActionScript 2.0 is not a new language. It is an enhancement to the previous version, by building on the existing language. In fact, Flash MX 2004 compiles AS2 into AS1 equivalent bytecodes. One reason for this is backwards compatibility in Flash Player 6. As a result, one can code in AS2 and compile it for Flash Player 6. For better optimization, target for Flash Player 6.0.65.0 or higher. Some version 2 components won’t run except in FP7, but some can run in 6.0.79.0 as well.
In terms of building applications, ActionScript 1.0 (and ECMAScript 3 in general) requires getting intimate with something called the prototype (and __proto__ if you’re a rebel trying to avoid unwanted side effects). The reason being that there was no ‘class’ construct, and inheritance was done in a very odd way.
Now in ActionScript 2.0, it is more suitable for OOP because of the following new keywords and features:
class, interface, extends, implements, private, public, dynamic, instrinsic, static, get, set, import; class path (similar to package), and strict data typing (useful in locating problems at compile time).
With these new features in ActionScript 2.0, building robust applications is becoming more attractive, and in a way easier. However, because Flash MX 2004 does not care if AS1 or AS2 is used (in most cases), one can still continue using AS1 and slowly migrate over to AS2.
The new WebServiceConnector component in Flash MX 2004 Professional makes talking to standard (SOAP) web services extremely easy. Here’s how to make a simple call to the BabelFish web service using Flash MX 2004 Professional’s new features:
Now let’s create the interface of the application:
Let’s bind the babelfish component to the interface:
Now is a good time to save the FLA.
Before we can make this work, we need to populate the ComboBox. First, let’s take a look at how the web interface of BabelFish looks like: http://babelfish.altavista.com/. From the dropdown menus, you can tell the languages and translation directions.
View Source from the browser, inspect the data that is sent to the server when an item is selected from the dropdown menu:
English to Chinese English to French English to German English to Italian English to Japanese English to Korean English to Portuguese English to Spanish Chinese to English French to English French to German German to English German to French Italian to English Japanese to English Korean to English Portuguese to English Russian to English Spanish to English
Let’s populate these data into our ComboBox: Deselect all items from the stage, and add a new script:
translationmode.addItem(({label:"English to Chinese", data:"en_zh"}));
translationmode.addItem(({label:"English to German", data:"en_de"}));
translationmode.addItem(({label:"English to Italian", data:"en_it"}));
translationmode.addItem(({label:"English to Japanese", data:"en_ja"}));
translationmode.addItem(({label:"English to Korean", data:"en_ko"}));
translationmode.addItem(({label:"English to Portuguese", data:"en_pt"}));
translationmode.addItem(({label:"English to Spanish", data:"en_es"}));
translationmode.addItem(({label:"Chinese to English", data:"zh_en"}));
translationmode.addItem(({label:"French to English", data:"fr_en"}));
translationmode.addItem(({label:"French to German", data:"fr_de"}));
translationmode.addItem(({label:"German to English", data:"de_en"}));
translationmode.addItem(({label:"German to French", data:"de_fr"}));
translationmode.addItem(({label:"Italian to English", data:"it_en"}));
translationmode.addItem(({label:"Japanese to English", data:"ja_en"}));
translationmode.addItem(({label:"Korean to English", data:"ko_en"}));
translationmode.addItem(({label:"Portuguese to English", data:"pt_en"}));
translationmode.addItem(({label:"Russian to English", data:"ru_en"}));
translationmode.addItem(({label:"Spanish to English", data:"es_en"}));
That’s it! Test movie and enter some text, select a translation mode, and click the Translate button to see the translated text! Not too bad is it? Try it out:
Okay, this is what it looks like. Why doesn’t it work? It’s because when the new Flash Player 7 is running inside a browser through HTTP, the new cross-domain security prevents this SWF from loading data from another domain.
What is needed is a policy file – an XML document specifying who is allowed, and this file has to reside at the web service domain. One way to get around this is to use a redirection proxy (server-side script) at this domain, to pass the data between servers and back to this translator. This will be the subject for another day.
UPDATE:
Instead of hardcoding the translation modes into the movie, Mark Shepherd of Macromedia suggested using the XMLConnector component to load an external XML file with the translation modes, and bind the data to the ComboBox. I’ve gone one step further by adding the web service URL in this XML document (BabelFish.xml). This is what I usually do for application configurations, it makes updating quick and easy without going into the source movie and recompiling another SWF.
Also, a redirection proxy file is being used. However, for some reason, this proxy only works when the movie is running inside Flash’s IDE or from the desktop standalone projector, but still not from this domain, even though both the SWF and the proxy are located in the same folder. This is the proxy similar to the one posted at Macromedia, except I’m using JScript instead of VBScript (that does not work either):
Why does this proxy work outside of the browser and not from the same domain? I’d really like to get an answer to this one.
You can download the source files, check them out and let me know if you find anything. Thanks!
Since ActionScript 2.0 does not have the “abstract” modifier, here’s one way to create a class that acts like an abstract class, by making the constructor private:
class PretendToBeAbstractClass {
// private constructor
private function PretendToBeAbstractClass() {}
}When the following statement is compiled, the compiler will complain that one can’t instantiate from this class because the constructor is private:
var o:PretendToBeAbstractClass = new PretendToBeAbstractClass();
Although the constructor is private, but because it behaves as protected, you can still extend this class:
class MyClass extends PretendToBeAbstractClass {
}
What is missing is the compiler does not actually know what an abstract class is; therefore there won’t be any warning messages.
As I mentioned in the last post, you can get around all the type-checking at runtime, and even instantiating an “abstract†class at runtime like this:
var o = new _global["PretendToBeAbstractClass"]();
Or even access “private†properties from it:
trace(o.somePrivateVar);
Obviously these actions defeat the purpose of strict-typing, but it is possible (until runtime type-checking is implemented).
Here’s one way to implement a Singleton in ActionScript 2.0:
class Singleton {
// the only instance of this class
private static var inst:Singleton;
// keep count of the number of Singleton objects referenced
private static var refCount:Number = 0;
// constructor is private
private function Singleton() {}
// get an instance of the class
public static function get instance():Singleton {
if (inst == null) inst = new Singleton();
++refCount;
return inst;
}
// return the number of instance references
public static function get referenceCount():Number {
return refCount;
}
}
The count property is for keeping count of the number of Singleton objects referenced (obviously it is not aware of destroyed objects), and is not really a necessary member of the Singleton pattern.
To use this class, one would write something like this:
var s1:Singleton = Singleton.instance;
var s2:Singleton = Singleton.instance;
Now s1 and s2 are the same instance of the Singleton class.
In ActionScript 2.0, there are “private” and “public” modifiers, but there is no “protected”. However, “private” behaves like “protected” – i.e. subclasses and instances can access private members; so there is no true private scope.
To make sure the compiler catches access to private properties/functions, strict-typing has to be used:
class SomeClass {
private var:somePrivateProperty:String;
}
// without specifying the type of the instance, the compiler will not
// prevent statements from accessing private properties; therefore,
// o.somePrivateProperty is accessible
var o = new SomeClass();
trace(o.somePrivateProperty);
// by specifying the type, the compiler will catch acess to
// private members:
var o:SomeClass = new SomeClass();
Because type-checking is only performed at compile time, there is no guarantee that private members cannot be accessed at runtime.
By default, if the “public” modifier is left out, the member is assumed to be public.
Welcome! This marks the first post for swfoo.com!
What is swfoo?
It’s about ActionScript 2.0 development, object-oriented programming, design patterns, software architecture, Rich Internet Applications, Flash, ColdFusion, Flash Remoting, web services, tips and tricks, life, the universe, and other geeky stuff…
What happens to Quantumwave.com?
[Update 2013, 10 years later: This domain is now qwmobile.com]
It is alive and kicking! Because Quantumwave Interactive Inc. is a company site that offers diverse services, it’d be better if the personal blog and Flash focus are kept separately. I’ll slowly migrate the Flash resources over to this site.
In the mean time, hope you’ll enjoy this new site (which is still under heavy construction)!
Dave Yang