Posts Tagged “flex”

01 11 2008

Extend a Singleton

Posted by: Romuald in experiments, tags: , , , ,

For a special purpose I had to extend a Singleton, to make my system fully flexible. I found complicated solutions that wasn't fully working as intended.

To use PureMVC, you have to extend a Singleton (Facade), which is the entry point of the framework. This is working only if you don't use the Facade class (the super Singleton) before using the subclass, otherwise you get an error, as the super singleton has already been instantiated.

Well this might be a simple solution but not working in my case.

First of all, they are a lot of solutions to correctly "lock" a Singleton, because in AS3, private constructor doesn't exist. Some of them have turn around, that you can solve with a bit more code, but the solution I prefer is instantiate the Singleton out of the constructor and method:

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Actionscript:
  1. private static var _instance:Singleton = new Singleton();

So, if I use the super singleton with a Singleton.getInstance(), and then use the subclass with a SingletonExtended.getInstance(), this will throw an error as when the SingletonExtended is called, the Singleton is called as well and has already been instantiated.

The solution I found is compare the super class name with a static class name, basically you can't use the keyword "this" when you declare a variable, but using "super" will return the same result (well that's odd but it is what I saw):

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Actionscript:
  1. private static var _className:String = getQualifiedClassName(super);

And then compare it with the super classname in the Singleton constructor:

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Actionscript:
  1. if (_instance != null && getQualifiedSuperclassName(this) != _className) throw new Error

if I trace(_className + " - " + getQualifiedSuperclassName(this)) in the Singleton constructor:

- when I use the Singleton class, I get: "null - Object"
- when I use the SingletonExtended class, I get: "Singleton - Singleton", meaning the constructor has been called from a subclass.

Until now, it is working pretty well, I can use:

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Actionscript:
  1. Singleton.getInstance().singletonValue
  2. SingletonExtended.getInstance().singletonValue
  3. SingletonExtended.getInstance().singletonExtendedValue

But we're not completely done. We can access to our two Singleton... but wait, "two Singleton", is that possible?

In fact, it is completely possible and it is even a problem. Let's say I have a undefined value in Singleton, like:

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Actionscript:
  1. private var _myValueNotInitialized:String;

And then you have a public method that is setting a value to this variable:

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Actionscript:
  1. public function initializeMyValue():void {
  2.     _myValueNotInitialized = "I am initialized";
  3. }

You can now use:

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Actionscript:
  1. Singleton.getInstance().initializeMyValue();
  2. or
  3. SingletonExtended.getInstance().initializeMyValue();

But here is the problem: you still have 2 instances. One in Singleton and the other in SingletonExtended. If you use:
Singleton.getInstance().initializeMyValue();
and trace:
SingletonExtended.getInstance().myValueNotInitialized
you will get null, which is normal.

This doesn't make a lot of sense for a Singleton, does it?

The solution I found is updating the Singleton instance with the SingletonExtended one.

In the Singleton, I'm now able to update the instance:

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Actionscript:
  1. public function updateInstance(instance:Singleton):void {
  2.     if (instance != null && instance is Singleton) _instance = instance;
  3.     else throw new Error("Incorrect Singleton update");
  4. }

And in the subclass SingletonExtended, I change the getInstance method:

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Actionscript:
  1. public static function getInstance():SingletonExtended {
  2.     Singleton.getInstance().updateInstance(_instance);
  3.     return _instance;
  4. }

This is doing the job I needed, a fully Extended Singleton with no errors accessing the super or he subclass.

I tried to break it, but if it is possible, I didn't find the hole. And if you have a better solution, I'd be very happy to see it.

You can download the source by clicking here, or see the classes below.

The main class:

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Actionscript:
  1. package {
  2.    
  3.     import flash.display.Sprite;
  4.    
  5.     /**
  6.      * <b>Author:</b> Romuald Quantin - <a href="http://www.soundstep.com/" target="_blank">www.soundstep.com</a><br />
  7.      * <b>Class version:</b> 1.0<br />
  8.      * <b>Actionscript version:</b> 3.0<br />
  9.      * <b>Date:</b> 11-2008<br />
  10.      */
  11.     
  12.     public class Main extends Sprite {
  13.        
  14.         //------------------------------------
  15.         // private properties
  16.         //------------------------------------
  17.        
  18.         //------------------------------------
  19.         // public properties
  20.         //------------------------------------
  21.        
  22.         //------------------------------------
  23.         // constructor
  24.         //------------------------------------
  25.        
  26.         public function Main() {
  27.            
  28.             trace("--- public properties ---");
  29.             trace(Singleton.getInstance().singletonValue + ">>> from Singleton");
  30.             trace(SingletonExtended.getInstance().singletonValue + ">>> from SingletonExtended");
  31.             trace(SingletonExtended.getInstance().singletonExtendedValue + ">>> from SingletonExtended");
  32.             trace(Singleton.getInstance().singletonValue + ">>> from Singleton");
  33.            
  34.             trace("--- access to public methods ---");
  35.             trace(Singleton.getInstance().publicSingletonMethod() + ">>> from Singleton");
  36.             trace(SingletonExtended.getInstance().publicSingletonMethod() + ">>> from SingletonExtended");
  37.             trace(SingletonExtended.getInstance().publicSingletonExtendedMethod() + ">>> from SingletonExtended");
  38.            
  39.             trace("--- access to private methods ---");
  40.             trace(Singleton.getInstance().accessPrivateSingletonMethod() + ">>> from Singleton");
  41.             trace(SingletonExtended.getInstance().accessPrivateSingletonMethod() + ">>> from SingletonExtended");
  42.             trace(SingletonExtended.getInstance().accessPrivateSingletonExtendedMethod() + ">>> from SingletonExtended");
  43.            
  44.             trace("--- access to protected and overriden methods ---");
  45.             trace(Singleton.getInstance().accessProtectedSingletonMethod() + ">>> from Singleton");
  46.             trace(SingletonExtended.getInstance().accessProtectedSingletonMethod() + ">>> from SingletonExtended");
  47.             trace(SingletonExtended.getInstance().accessOverridenSingletonExtendedMethod() + ">>> from SingletonExtended");
  48.            
  49.             trace("--- value not initialized ---");
  50.             trace("before = ", Singleton.getInstance().myValueNotInitialized);
  51.             Singleton.getInstance().initializeMyValue(); // or SingletonExtended.getInstance().initializeMyValue();
  52.             trace("after = ", Singleton.getInstance().myValueNotInitialized);
  53.            
  54.             // this will generate errors
  55.             // as you can't instantiate twice a Singleton or a sublass of Singleton
  56.            
  57.             //var s1:Singleton = new Singleton();
  58.             //var s2:SingletonExtended = new SingletonExtended();
  59.            
  60.         }
  61.        
  62.         //
  63.         // PRIVATE, PROTECTED
  64.         //________________________________________________________________________________________________
  65.        
  66.         //
  67.         // PUBLIC
  68.         //________________________________________________________________________________________________
  69.        
  70.     }
  71. }

The Singleton class:

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Actionscript:
  1. package {
  2.  
  3.     import flash.utils.getQualifiedClassName;
  4.     import flash.utils.getQualifiedSuperclassName;
  5.  
  6.     /**
  7.      * <b>Author:</b> Romuald Quantin - <a href="http://www.soundstep.com/" target="_blank">www.soundstep.com</a><br />
  8.      * <b>Class version:</b> 1.0<br />
  9.      * <b>Actionscript version:</b> 3.0<br />
  10.      * <b>Date:</b> 11-2008<br />
  11.      */
  12.     
  13.     public class Singleton {
  14.        
  15.         //------------------------------------
  16.         // private properties
  17.         //------------------------------------
  18.        
  19.         private static var _instance:Singleton = new Singleton();
  20.         private static var _className:String = getQualifiedClassName(super);
  21.        
  22.         private var _myValueNotInitialized:String;
  23.        
  24.         //------------------------------------
  25.         // public properties
  26.         //------------------------------------
  27.        
  28.         public var singletonValue:String = "Singleton value";
  29.        
  30.         //------------------------------------
  31.         // constructor
  32.         //------------------------------------
  33.        
  34.         public function Singleton() {
  35.             if (_instance != null && getQualifiedSuperclassName(this) != _className) throw new Error("Singleton is obviously... Singleton.");
  36.         }
  37.        
  38.         //
  39.         // PRIVATE, PROTECTED
  40.         //________________________________________________________________________________________________
  41.        
  42.         private function privateSingletonMethod():String {
  43.             return "privateSingletonMethod";
  44.         }
  45.        
  46.         protected function protectedSingletonMethod():String {
  47.             return "protectedSingletonMethod";
  48.         }
  49.        
  50.         //
  51.         // PUBLIC
  52.         //________________________________________________________________________________________________
  53.        
  54.         public function initializeMyValue():void {
  55.             _myValueNotInitialized = "I am initialized";
  56.         }
  57.        
  58.         public function updateInstance(instance:Singleton):void {
  59.             if (instance != null && instance is Singleton) _instance = instance;
  60.             else throw new Error("Incorrect Singleton update");
  61.         }
  62.  
  63.         public static function getInstance():Singleton {
  64.             return _instance;
  65.         }
  66.        
  67.         public function publicSingletonMethod():String {
  68.             return "publicSingletonMethod value";
  69.         }
  70.        
  71.         public function accessPrivateSingletonMethod():String {
  72.             return privateSingletonMethod();
  73.         }
  74.        
  75.         public function accessProtectedSingletonMethod():String {
  76.             return protectedSingletonMethod();
  77.         }
  78.        
  79.         public function get myValueNotInitialized():String {
  80.             return _myValueNotInitialized;
  81.         }
  82.     }
  83. }

The SingletonExtended class:

Plain Text
Actionscript:
  1. package {
  2.  
  3.     /**
  4.      * <b>Author:</b> Romuald Quantin - <a href="http://www.soundstep.com/" target="_blank">www.soundstep.com</a><br />
  5.      * <b>Class version:</b> 1.0<br />
  6.      * <b>Actionscript version:</b> 3.0<br />
  7.      * <b>Date:</b> 11-2008<br />
  8.      */
  9.     
  10.     public class SingletonExtended extends Singleton {
  11.        
  12.         //------------------------------------
  13.         // private properties
  14.         //------------------------------------
  15.        
  16.         private static var _instance:SingletonExtended = new SingletonExtended();
  17.        
  18.         //------------------------------------
  19.         // public properties
  20.         //------------------------------------
  21.        
  22.         public var singletonExtendedValue:String = "SingletonExtended value";
  23.        
  24.         //------------------------------------
  25.         // constructor
  26.         //------------------------------------
  27.        
  28.         public function SingletonExtended() {
  29.             if (_instance != null) throw new Error("SingletonExtended is obviously also... Singleton.");
  30.         }
  31.        
  32.         //
  33.         // PRIVATE, PROTECTED
  34.         //________________________________________________________________________________________________
  35.        
  36.         private function privateSingletonExtendedMethod():String {
  37.             return "privateSingletonExtendedMethod";
  38.         }
  39.        
  40.         override protected function protectedSingletonMethod():String {
  41.             return "protectedSingletonMethod overriden in SingletonExtended, value in super.protectedSingletonMethod(): " + super.protectedSingletonMethod();
  42.         }
  43.        
  44.         //
  45.         // PUBLIC
  46.         //________________________________________________________________________________________________
  47.        
  48.         public static function getInstance():SingletonExtended {
  49.             Singleton.getInstance().updateInstance(_instance);
  50.             return _instance;
  51.         }
  52.        
  53.         public function publicSingletonExtendedMethod():String {
  54.             return "publicSingletonExtendedMethod value";
  55.         }
  56.        
  57.         public function accessPrivateSingletonExtendedMethod():String {
  58.             return privateSingletonExtendedMethod();
  59.         }
  60.        
  61.         public function accessOverridenSingletonExtendedMethod():String {
  62.             return protectedSingletonMethod();
  63.         }
  64.    
  65.     }
  66. }

Comments No Comments »

11 10 2008

Flex SDK 3.1 bug with SWC and GenericTag (fix update)

Posted by: Romuald in talking, tags: , ,

Hi,

In this previous post talking about a bug with the Flex SDK, you can find how to fix a problem when you compile a SWF including a SWC containing pictures.

Actually the version of the Flex SDK is 3.1 and the structure of the java library slightly changed. I applied the same fix on the GenericTag java class but now this class is in the jar file swfutils.jar

You just need to replace this jar with the fix in this location:

/flex_sdk/lib/

Click here to get the jar fixed

Comments No Comments »

23 06 2008

Flash liquid layout with BaseUI version 2

Posted by: Romuald in BaseUI, tags: , , , , , , ,

I've been working on the second version of BaseUI, so I'm happy to release it today.

THIS IS NOT AN UPDATE.

This new version is quite different, as well as the syntax, so the code you have written for the previous version won't work with this one.

I didn't try it yet in a real project but you shouldn't find too much bugs, comment if you find some, I'll solve them.

I've been working a lot with Flex and everyone enjoy a lot the layouts I think. I build this new version taking a lot of features from Flex. In the demo I use the Flex Builder interface to set the properties on a DisplayObject, so it is working pretty much the same.

I didn't build the Flex layouts obviously, but I'm thinking about it. Anyway, BaseUI allows you to use those following properties on a DisplayObject:

x, y, left, right, top, bottom, width, height, horizontalCenter, verticalCenter, ratio, alignX, alignY

You'll discover some nice features, for example you can use Number or String to set the properties. I've done that because you can now use percentage value for the width and the height!

This will make you able to do a lot more things, have a try in the demo.

Here is some examples of the new syntax:

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Actionscript:
  1. var baseUI:BaseUI = new BaseUI(this);
  2. var element:ElementUI = baseUI.add(mySprite);
  3. element.right = 10;
  4. element.bottom = "10";
  5. element.width = "50%"
  6. element.height = 200;
  7. addChild(mySprite);

Plain Text
Actionscript:
  1. var baseUI:BaseUI = new BaseUI(this);
  2. var element:ElementUI = baseUI.add(mySprite);
  3. element.properties = {right:10, verticalCenter:0};
  4. addChild(mySprite);

Plain Text
Actionscript:
  1. var baseUI:BaseUI = new BaseUI(this);
  2. var element:ElementUI = baseUI.add(mySprite);
  3. element.ratio = ElementUI.RATIO_IN;
  4. addChild(mySprite);

As the previous version, if you use the onStage property set to false (to set the reference on the parent instead of the stage), everything will work except the "ratio in" and "ratio out". I need to build a Layout class for that, probably the next step.

A memory system has been included to make your life easier if you need to switch between properties.
For example, if your width is set to 200 or "50%", and later you set a left and right version values. The width is not used anymore as it doesn't make sense, but the value is "memorized" and will be set back automatically if needed, if you set an horizontalCenter value for example. This is done internally, you don't have to do anything.

Have a look at the demo and you'll understand what I mean by values "memorized", basically it is working like the Flex Builder interface.

A tutorial will follow when I get a chance.

If you find any bugs, if you have some ideas to improve it or if you just want to talk about, please comment.

Here is the demo, the docs and the source.

Comments 10 Comments »

10 06 2008

Flex SDK 3 bug with SWC and GenericTag

Posted by: Romuald in talking, tags: , , ,

I recently used ANT and compc to compile a SWC. I had to include another SWC with classes and jpg and some other classes as I needed to force them at compile-time to make the getDefinitionByName class working.

If you don't know getDefinitionByName (and registerClassAlias and getClassByAlias), it make us able to create instances of classes with a string (from a XML for example). The problem is the compiler doesn't include them at compile-time if they are not used.

You will find tons of people talking about that if you google it.

One trick is add a public var myClass:MyClass = null; in the code or use a array. Not really ideal as you have to do that for every class. Example:

Plain Text
Actionscript:
  1. public var myClassPage:MyClassPage = null;
  2. var PageClass:Class = getDefinitionByName("com.site.page.MyClassPage") as Class;
  3. var page:SuperClassPage = new PageClass();

Here is a class that will help you manage that if you need:

Plain Text
Actionscript:
  1. package com.soundstep.managers {
  2.    
  3.     import com.site.menu.basic.*;
  4.     import com.site.page.*;
  5.     import flash.net.*;
  6.  
  7.     /**
  8.      * <b>Author:</b> Romuald Quantin - <a href="http://www.soundstep.com/" target="_blank">www.soundstep.com</a><br />
  9.      * <b>Class version:</b> BETA 1.0<br />
  10.      * <b>Actionscript version:</b> 3.0<br />
  11.      * <b>Copyright:</b>
  12.      * <br />
  13.      * <b>Date:</b> 05-2008<br />
  14.      * <b>Usage:</b>
  15.      * @example
  16.      * <listing version="3.0"></listing>
  17.      */
  18.    
  19.     public class ImportManager {
  20.  
  21.         //------------------------------------
  22.         // private, protected properties
  23.         //------------------------------------
  24.        
  25.         private static var INITIALIZED:Boolean = false;
  26.        
  27.         private static var importManager:ImportManager = new ImportManager();
  28.         private static var importer:Array = [
  29.             BasicMenu,
  30.             Home,
  31.             Page1,
  32.             Page2,
  33.             Page3,
  34.             Page4,
  35.             Page5,
  36.             PageSub21,
  37.             PageSub211,
  38.             PageSub22,
  39.             PageSub221,
  40.             PageSub222,
  41.             PageSub223,
  42.             PageSub23,
  43.             PageSub231,
  44.             PageSub232,
  45.             PageSub233,
  46.             PageSub31,
  47.             PageSub311,
  48.             PageSub32,