8.1. Objects and Shared Objects
ActionScript
objects are implemented as associative arrays. Each object property
associates a value with a property name. The property name is a
string that is used to store and retrieve a value in a slot, or
location, within the object. Objects are similar to arraysthey
have slots that hold values. Arrays are designed to provide access to
the value in each slot via an index number, while objects provide
access to values via a string property name. Example 8-1 reviews how to add
properties to a
generic ActionScript object.
Example 8-1. Creating and adding properties to an ActionScript object
// Create a simple object named user.
user = new Object( );
// Use dot notation to add a userName property.
user.userName = "blesser";
// Use the [] operator to add a password property.
user["password"] = "bigSecret";
// Add a function as a property of this generic object.
user.showProperties = function ( ) {
for (var prop in this) {
trace(prop + ": " + this[prop]);
}
};
// Call the function.
user.showProperties( );
// Output to the Output panel for this script:
showProperties: [type Function]
password: bigSecret
userName: blesser
In ActionScript, objects are the foundation on which custom classes
are built. However the SharedObject class cannot
be extended the same way as other classes. Shared objects always
store data in a simple associative array. Shared objects can contain
instances of other classes in their slots (i.e.,
properties); however, there are some restrictions on the type of data
that can be stored in a shared object's slots. With
one exception, a shared object slot can contain any native
ActionScript type such as a Number,
String, Date,
Boolean, Object, or
Array. However, an LSO cannot be used to store
and retrieve a function in a later session, and RSOs cannot make a
function available to remote movies by assigning one to a slot.
However, with an added step of registering a class in a movie, a
shared object slot can contain custom classes, provided they are also
defined in each Flash movie or in the server-side application where
they are accessed.
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