Flash 8 ActionScript 2.0 Language Reference

Class SharedObject

Object

Here are three possible uses of shared objects:

• A game that stores a user's high scores. The game could provide personalized data for users, such as user name and high score, without dedicating storage on the server.
• A phone book application that can work either online or offline. The phone book, delivered as a projector application, could contain a local data cache with a list of names and phone numbers entered by the user. When an Internet connection is available, the application would retrieve up-to-date information from a server. When no connection is available, the application would use the latest data saved in shared objects.
• User preferences or tracking data for a complex website, such as a record of which articles a user read on a news site. Tracking this information would allow you to display articles that have already been read differently from new, unread articles. Storing this information on the user's computer reduces server load.

Local shared objects maintain local persistence. For example, you can call SharedObject.getLocal() to create a shared object that contains the high score in a game. Because the shared object is locally persistent, Flash saves its data attributes on the user's computer when the game is closed. The next time the game is opened, the high score from the previous session is displayed. Alternatively, you could set the shared object's properties to null before the game is closed. The next time the SWF file runs, the game opens without the previous high score.

To create a local shared object, use the following syntax:

var so:SharedObject = SharedObject.getLocal("userHighScore");
so.data.highScore = new Number();
so.flush();

In the example, the shared object is explicitly flushed, or written to a disk. When an application closes, shared objects are automatically flushed; however, it is shown here to demonstrate the step of writing data to a disk.

Local disk space considerations: Local shared objects can be very useful, but they have some limitations that are important to consider as you design your application. Sometimes your SWF files may not be allowed to write local shared objects, and sometimes the data stored in local shared objects can be deleted without your knowledge. Flash Player users can manage the disk space that is available to individual domains or to all domains. When users lower the amount of disk space available, some local shared objects may be deleted. Flash Player users also have privacy controls that can prevent third-party domains (domains other than the domain in the current browser address bar) from reading or writing local shared objects.

Note: Local content can always write third-party shared objects to disk, even if writing of shared objects to disk by third-party domains is disallowed.

Macromedia recommends that you check for failures that are related to the amount of disk space available and to user privacy controls. Perform these checks when you call getLocal() and flush():

• SharedObject.getLocal() — This method returns null when the user has disabled third-party shared objects and the domain of your SWF file does not match the domain in the browser address bar.

• SharedObject.flush() — This method returns false when the user has disabled shared objects for your domain or for all domains. It returns "pending" when additional storage space is needed and the user must interactively decide whether to allow an increase.

If your SWF file attempts to create or modify local shared objects, make sure that your SWF file is at least 215 pixels wide and at least 138 pixels high (the minimum dimensions for displaying the dialog box that prompts users to increase their local shared object storage limit). If your SWF file is smaller than these dimensions and an increase in the storage limit is required, SharedObject.flush() fails, returning "pending" but then calling your SharedObject.onStatus handler with a result of "SharedObject.Flush.Failed".

data Property

public data : Object

var items_array:Array = new Array(101, 346, 483);
var currentUserIsAdmin:Boolean = true;
var currentUserName:String = "Ramona";

var my_so:SharedObject = SharedObject.getLocal("superfoo");
my_so.data.itemNumbers = items_array;
my_so.data.adminPrivileges = currentUserIsAdmin;
my_so.data.userName = currentUserName;

for (var prop in my_so.data) {
    trace(prop+": "+my_so.data[prop]);
}

All attributes of a shared object's data property are saved if the object is persistent, and the shared object contains the following information:

userName: Ramona
adminPrivileges: true
itemNumbers: 101,346,483

Note: Do not assign values directly to the data property of a shared object, as in so.data = someValue; Flash ignores these assignments.

To delete attributes for local shared objects, use code such as delete so.data.attributeName; setting an attribute to null or undefined for a local shared object does not delete the attribute.

To create private values for a shared object--values that are available only to the client instance while the object is in use and are not stored with the object when it is closed--create properties that are not named data to store them, as shown in the following example:

var my_so:SharedObject = SharedObject.getLocal("superfoo");
my_so.favoriteColor = "blue";
my_so.favoriteNightClub = "The Bluenote Tavern";
my_so.favoriteSong = "My World is Blue";

for (var prop in my_so) {
    trace(prop+": "+my_so[prop]);
}

The shared object contains the following data:

favoriteSong: My World is Blue
favoriteNightClub: The Bluenote Tavern
favoriteColor: blue
data: [object Object]

// Create a listener object and function for the <enter> event.
var textListener:Object = new Object();
textListener.enter = function(eventObj:Object) {
    my_so.data.myTextSaved = eventObj.target.text;
    my_so.flush();
};

onStatus Event Handler

public onStatus = function(infoObject:Object) {}

The information object has a code property containing a string that describes the result of the onStatus handler, and a level property containing a string that is either "Status" or "Error".

In addition to this onStatus handler, Flash also provides a super function called System.onStatus. If onStatus is invoked for a particular object and no function is assigned to respond to it, Flash processes a function assigned to System.onStatus, if it exists.

The following events notify you when certain SharedObject activities occur:

var message_str:String;
this.createTextField("message_txt", this.getNextHighestDepth(), 0, 0, 300, 22);
message_txt.html = true;
this.createTextField("status_txt", this.getNextHighestDepth(), 10, 30, 300, 100);
status_txt.multiline = true;
status_txt.html = true;

var items_array:Array = new Array(101, 346, 483);
var currentUserIsAdmin:Boolean = true;
var currentUserName:String = "Ramona";
var my_so:SharedObject = SharedObject.getLocal("superfoo");
my_so.data.itemNumbers = items_array;
my_so.data.adminPrivileges = currentUserIsAdmin;
my_so.data.userName = currentUserName;

my_so.onStatus = function(infoObject:Object) {
    status_txt.htmlText = "<textformat tabStops='[50]'>";
    for (var i in infoObject) {
        status_txt.htmlText += "<b>"+i+"</b>"+"\t"+infoObject[i];
    }
    status_txt.htmlText += "</textformat>";
};
            
var flushResult = my_so.flush(1000001);
switch (flushResult) {
case 'pending' :
    message_str = "flush is pending, waiting on user interaction.";
    break;
case true :
    message_str = "flush was successful. Requested storage space approved.";
    break;
case false :
    message_str = "flush failed. User denied request for additional storage.";
    break;
}
message_txt.htmlText = "<a href=\"asfunction:System.showSettings,1\
"><u>"+message_str+"</u></a>";

The MovieClip.getNextHighestDepth() method used in this example requires Flash Player 7 or later. If your SWF file includes a version 2 component, use the version 2 components DepthManager class instead of the MovieClip.getNextHighestDepth() method.

clear Method

public clear() : Void

var my_so:SharedObject = SharedObject.getLocal("superfoo");
my_so.data.name = "Hector";
trace("before my_so.clear():");
for (var prop in my_so.data) {
    trace("\t"+prop);
}
trace("");
my_so.clear();
trace("after my_so.clear():");
for (var prop in my_so.data) {
    trace("\t"+prop);
}

This ActionScript displays the following message in the Output panel:This ActionScript writes the following message to the log file:

before my_so.clear():
    name

after my_so.clear():

flush Method

public flush([minDiskSpace:Number]) : Object

If this method returns "pending", Flash Player shows a dialog box asking the user to increase the amount of disk space available to objects from this domain. To allow space for the shared object to grow when it is saved in the future, which avoids return values of "pending", pass a value for minimumDiskSpace. When Flash tries to write the file, it looks for the number of bytes passed to minimumDiskSpace, instead of looking for enough space to save the shared object at its current size.

For example, if you expect a shared object to grow to a maximum size of 500 bytes, even though it might start out much smaller, pass 500 for minimumDiskSpace. If Flash asks the user to allot disk space for the shared object, it asks for 500 bytes. After the user allots the requested amount of space, Flash won't have to ask for more space on future attempts to flush the object (as long as its size doesn't exceed 500 bytes).

After the user responds to the dialog box, this method is called again and returns either true or false; SharedObject.onStatus is also invoked with a code property of SharedObject.Flush.Success or SharedObject.Flush.Failed.

For more information, see "Local disk space considerations" in the SharedObject class overview.

this.syncSettingsCore = function(soName:String, override:Boolean, settings:Object) {
    var my_so:SharedObject = SharedObject.getLocal(soName, "http://www.mydomain.com/app/sys");
    // settings list index
    var i;
    // For each specified value in settings:
    // If override is true, set the persistent setting to the provided value.
    // If override is false, fetch the persistent setting, unless there
    // isn't one, in which case, set it to the provided value.
    for (i in settings) {
    if (override || (my_so.data[i] == null)) {
        my_so.data[i] = settings[i];
    } else {
        settings[i] = my_so.data[i];
    }
    }
    my_so.flush(1000);
};

getLocal Method

public static getLocal(name:String, [localPath:String], [secure:Boolean]) : SharedObject

var so:SharedObject = SharedObject.getLocal("savedData")

Note: If the user has selected to never allow local storage for this domain, the object is not saved locally, even if a value for localPath is specified. The exception to this rule is local content. Local content can always write shared objects from third-party domains (domains other than the domain in the current browser address bar) to disk, even if writing of third-party shared objects to disk is disallowed.

To avoid name collisions, Flash looks at the location of the SWF file that is creating the shared object. For example, if a SWF file at www.myCompany.com/apps/stockwatcher.swf creates a shared object named portfolio, that shared object does not conflict with another object named portfolio that was created by a SWF file at www.yourCompany.com/photoshoot.swf because the SWF files originate from different directories.

Although the localPath parameter is optional, you should give some thought to its use, especially if other SWF files need to access the shared object. If the data in the shared object is specific to one SWF file that will not be moved to another location, then use of the default value makes sense. If other SWF files need access to the shared object, or if the SWF file that creates the shared object will later be moved, then the value of this parameter affects whether any SWF files are able to access the shared object. For example, if you create a shared object with localPath set to the default value of the full path to the SWF file, then no other SWF file can access that shared object. If you later move the original SWF file to another location, then not even that SWF file can access the data already stored in the shared object.

You can reduce the likelihood that you will inadvertently restrict access to a shared object by using the localpath parameter. The most permissive option is to set the localPath parameter to "/", which makes the shared object available to all SWF files in the domain, but increases the likelihood of name collisions with other shared objects in the domain. More restrictive options are available to the extent that you can append the localPath parameter with folder names that are contained in the full path to the SWF file; for example, your localPath parameter options for the portfolio shared object created by the SWF file at www.myCompany.com/apps/stockwatcher.swf are: "/"; "/apps"; and "/apps/stockwatcher.swf". You need to determine which option provides optimal flexibility for your application.

When using this method, consider the Flash Player security model:

• You cannot access shared objects across sandbox boundaries.
• Users can restrict shared object access via the Flash Player Settings dialog box, or the Settings Manager. By default, shared objects can be created up to a maximum of 100K of data per domain. Administrative users and users can also place restrictions on the ability to write to the file system.

If you publish SWF file content to be played back as local files (either locally installed SWF files or projectors [EXE]), and you need to access a specific shared object from more than one local SWF file, be aware that for local files, two different locations may be used to store shared objects. The domain that is used depends on the security permissions granted to the local file that created the shared object. Local files can have three different levels of permissions: 1) access to the local filesystem only, 2) access to the network only, or 3) access to both the network and the local filesystem. Local files with access to the local filesystem (either 1 or 3) store their shared objects in one location. Local files with no access to the local filesystem (2) store their shared objects in another location. For more information, see the following:

• "Understanding Security" in Learning ActionScript 2.0 in Flash
• The Flash Player 8 Security white paper at http://www.macromedia.com/go/fp8_security
• The Flash Player 8 Security-Related API white paper at http://www.macromedia.com/go/fp8_security_apis

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// Create the shared object and set localpath to server root.
var my_so:SharedObject = SharedObject.getLocal("savedText", "/");
// Load saved text from the shared object into the myText_ti TextInput component.
myText_ti.text = my_so.data.myTextSaved;
// Assign an empty string to myText_ti if the shared object is undefined
// to prevent the text input box from displaying "undefined" when
// this script is first run.
if (myText_ti.text == undefined) {
    myText_ti.text = "";
}
// Create a listener object and function for <enter> event
var textListener:Object = new Object();
textListener.enter = function(eventObj:Object) {
    my_so.data.myTextSaved = eventObj.target.text;
    my_so.flush();
};
// Register the listener with the TextInput component instance
myText_ti.addEventListener("enter", textListener);

// Get the kookie
var my_so:SharedObject = SharedObject.getLocal("kookie");

// Get the user of the kookie and go to the frame number saved for this user.
if (my_so.data.user != undefined) {
    this.user = my_so.data.user;
    this.gotoAndStop(my_so.data.frame);
}

// On each frame, call the rememberme function to save the frame number.
function rememberme() {
    my_so.data.frame=this._currentframe;
    my_so.data.user="John";
}

getSize Method

public getSize() : Number

Flash calculates the size of a shared object by stepping through all of its data properties; the more data properties the object has, the longer it takes to estimate its size. Estimating object size can take significant processing time, so you may want to avoid using this method unless you have a specific need for it.

var items_array:Array = new Array(101, 346, 483);
var currentUserIsAdmin:Boolean = true;
var currentUserName:String = "Ramona";

var my_so:SharedObject = SharedObject.getLocal("superfoo");
my_so.data.itemNumbers = items_array;
my_so.data.adminPrivileges = currentUserIsAdmin;
my_so.data.userName = currentUserName;

var soSize:Number = my_so.getSize();
trace(soSize);