Programming Flash Communication Server

This is the Title of the Book, eMatter Edition

Copyright © 2007 O’Reilly & Associates, Inc. All rights reserved.

Differences Between Flash ActionScript and Server-Side ActionScript

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An excellent discussion of object-oriented programming and prototype-based inher-

itance using JavaScript is available in JavaScript: The Definitive Guide, Fourth Edition

(O’Reilly) by David Flanagan. Flanagan’s book is especially useful for server-side

scripting as it covers JavaScript 1.5—the exact same language as SSAS.

Prototype-based inheritance issues in Flash 5 and Flash MX and the various options

for implementing inheritance without using super in Flash are discussed in detail

here:

http://www.quantumwave.com/flash/inheritance.html

While the discussion centers around Flash, it is also a valuable resource for server-

side scripting.

Many of the communication objects available cannot be subclassed using these sorts

of techniques. For example, shared objects are not created by calling a constructor

function. Instead, they are created via a static method such as SharedObject.getRem-

ote( ) on the client or get( ) on the server. Often there are better ways to work with

the communication classes than inheriting from them. See Chapter 15 for more

details.

Single Execution Context

Client-side ActionScript provides a special _global object that provides a place to

store global variables that exist outside the scope of the timeline. For example:

// Assume a _global object already exists.

_global.x = 3; // OK in client-side AS; however, error in SSAS.

trace (x); // Will output: 3 in Flash MX and later.

In client-side ActionScript, if a variable is not found on the timeline and the _global

object has a property of the same name, the _global object’s property is accessed.

In SSAS there are no timelines. All server-side code executes in one global context

that is associated with each application instance. So there is little point to providing a

special

_global object. You can create an object named _global, but it will not work

as it does in client-side ActionScript. In general, you should avoid creating an object

named

_global in SSAS because it doesn’t add anything and may create problems if

you are using Flash Remoting (see Chapter 11).

When loaded into a main.asc file, the netservices.asc file creates a new

_global object

and assigns properties to it. The RecordSet.asc file also adds properties to the

_global

object. Furthermore, netservices.asc adds the unshift( ) and registerClass( ) methods to

the Object class; since all classes inherit from Object, every object shows these meth-

ods when its properties are enumerated with a for-in loop. Chapter 11 contains addi-

tional information on dealing with these inconveniences. If you must use a

_global

object in SSAS, you should check whether it already exists before creating your own

and be careful to avoid collisions with the

_global properties defined in netservices.asc.