Understanding AS3 shared objects

December 28, 2008 • Actionscript 3, Flash by Emanuele Feronato • 16 Comments

This is the AS3 version of Managing savegames with Flash shared objects.

In this post I’ll explain the basic of shared objects, then later I’ll add the feature to Designing the structure of a Flash game – AS3 version in order to have a game template more complete.

Let’s start with the result: that’s what we are going to create:

As you will see, the counter increases when you reload the page.

Let’s take a look at the script:

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package {
	import flash.display.Sprite;
	import flash.net.SharedObject;
	import flash.text.*;
	public class as3_shared_objects extends Sprite {
		var shared:SharedObject;
		public function as3_shared_objects() {
			shared = SharedObject.getLocal("reloaded");
			if (shared.data.visits==undefined) {
				shared.data.visits = 1;
			}
			else {
				shared.data.visits ++;
			}
			show_text(shared.data.visits);
			shared.close();
		}
		public function show_text(str) {
			var shared_text:TextField = new TextField();
			var format:TextFormat = new TextFormat();
			format.font = "Lucida Console";
			format.color = 0xffff00;
			shared_text.width = 300;
			shared_text.defaultTextFormat = format;
			shared_text.x = 25;
			shared_text.y = 15;
			addChild(shared_text);
			shared_text.appendText("You visited this page "+str+" times");
		}
	}
}

Line 3: importing the class handling shared objects

Line 6: declaring a SharedObject variable called shared

Line 8: getLocal() returns a reference to a locally persistent shared object (in this case reloaded) that is available only to the current client. If the shared object does not already exist, getLocal() creates one.

Lines 9-11: when looking at the visits value inside the shared ojbect, I set it to 1 if it’s undefined (it’s the first time I am executing the script)

Lines 12-14: if visits is not undefined, it’s not the first time I am executing the script, so I have to increment its value

Line 16: closing the shared object. Some docs say you may experience problems if you don’t close it… I tried and I haven’t any… but I am closing it anyway…

Download the source code

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This post has 16 comments

  1. Orion

    on December 28, 2008 at 9:00 pm

    So how to make something like ‘this site has been visited total of x times?

  2. Jack Hopkins

    on December 29, 2008 at 7:40 pm

    you could use javascript, there are many scripts on the ‘net
    good tut!

  3. Pixelero

    on January 2, 2009 at 1:58 pm

    Somehow if I update this by clicking on the headline ‘Understanding AS3 shared objects’ above, the counter increases by 2 ? – on a normal ‘F5′ browser update works correctly, and adds just 1.

  4. real reason

    on January 4, 2009 at 1:02 pm

    To Orion: that isn’t the real reason he did this, it is there to show how u can have an update finished, for example: instead of updating each time u load it, it is updated each time that a level is finished, and it becomes the level number, not to show how many times u visit the page

  5. Designing the structure of a Flash game - AS3 version - Part 3 : Emanuele Feronato

    on January 16, 2009 at 12:33 pm

    [...] Moreover, I made some code optimization and now you can only play levels you already completed and the first uncompleted level, thanks to AS3 shared objects. [...]

  6. Danny

    on February 16, 2009 at 11:00 am

    Very good, but dude, please change your logo back to the old one.

    I know that you paid money for this one, but you have to take the loss on the chin!

    Great blog though :)

  7. Tutorial: Sharing shared objects between games/applications « the keg’o'grog blog

    on June 6, 2009 at 5:47 pm

    [...] youself familiar with Saving and Loading in Flash by reading this tutorial or this tutorial. Thanks to Michael and Emanuele for this. You should also bookmark their blogs, these guys are [...]

  8. Flash for Thought « Interactive Design II

    on October 14, 2009 at 5:21 am

    [...] http://www.emanueleferonato.com/2008/12/28/understanding-as3-shared-objects/ [...]

  9. Oct 22 Week 04 Make Up Class « Flash For Artists

    on October 22, 2009 at 9:24 pm

    [...] http://www.emanueleferonato.com/2008/12/28/understanding-as3-shared-objects/ [...]

  10. Broxter

    on January 14, 2010 at 4:40 pm

    Thanks a lot! Just what I was looking for.

  11. Complete Flash Sokoban game in less than 2KB - Emanuele Feronato

    on May 19, 2010 at 3:54 pm

    [...] 10 levels * Tiles of different color and shape * Shared objects to save the games * Eye-candy effects (being only 2KB!!) to show completed levels and current level [...]

  12. Code snippets for the future « Jon Reids FMP

    on December 19, 2010 at 7:11 pm

    [...] be looking at this post to help me understand shared objects, and handily, adobe have posted up all the chapters of AS3 [...]

  13. Rennan

    on January 11, 2011 at 7:40 pm

    I´ve made this class based on your post. It´s simple. But, maybe it help someone. If someone have some idea, please, implement it.

    package
    {
    import flash.net.SharedObject;

    public class SavePoint
    {
    private static var shared:SharedObject = SharedObject.getLocal(“save_point”);

    public function SavePoint ()
    {

    }
    public static function Save (object:Object):void
    {
    if (object!=null)
    {
    shared.data.box = object;
    }
    else
    {
    Erase ();
    trace (“Error – Argument ‘object’ can not receive null values!”);
    }
    }
    public static function Load ():Object
    {
    var obj:Object = shared.data.box;
    return obj;
    }
    public static function Erase ():void
    {
    shared.clear ();

    }
    public static function Update (object:Object):void
    {
    // TODO
    }
    }
    }

  14. Simon

    on February 11, 2011 at 4:21 pm

    Can someone help me please, I’m struggling with this coding, it’s a simple cookie (LSO) detection system but I can’t get it to run with writing the text below no matter what I try.

    // Create Flash Cookie (LSO)
    var cookie:SharedObject = SharedObject.getLocal(“SiteLog”);
    // first visit, i.e, cookie hasn’t been set
    if (cookie.data.played == undefined)
    {
    // set cookie to true
    cookie.data.played = true;
    cookie.flush(); // write the data
    trace(“Data written, first visit”);
    }
    else
    {
    // return visit

    trace(“Data acknowleged, return trip to site”);
    }
    // clear the Shared Object for testing

    function clearCookie(evt:MouseEvent):void {
    cookie.clear();
    trace(“Cookie Removed”);
    };
    clearCookie_btn.addEventListener(MouseEvent.CLICK, clearCookie);

    - I want to have this come on screen after it’s loaded for the second time :

    var txt:TextField = new TextField();
    txt.text = “Republic of Code”;
    addChild(txt);

    Any help would be great.

  15. Criando a estrutura de um jogo em flash – 3ª parte « Tentativa de Programação

    on April 30, 2011 at 6:25 am

    [...] que até onde entendi, funciona +- como cookies de navegação. Tem alguma explicação nesse guia aqui e também tem os meus comentários no código fonte que vou disponibilizar logo abaixo, lá tem [...]

  16. diego nunes

    on June 6, 2011 at 1:11 pm

    . . I though it would be worth to mention that the “close” method is only appliable to Remote Shared Objects. Since you’re using “getLocal” for a locally stored Shared Object, you really don’t need it.
    . . Using “flush”, on the other hand, to explicitly persist the data, would be helpful to avoid any problem if the flash gets force closed.

    . Amplexos.

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