If you need to do any sort of parameter passing to your AS3 or Flex Swf’s you may be wondering how to do it. In the olden days when you had a _root context on your MovieClips, and thank you very much there were your variables ready and waiting when you loaded your SWF.

Flex / AS3 has a more semantic and structured approach to the problem, well, it puts the values somewhere more semantic and structured at least.

If your application entry point is a subclass of Application you can grab your parameters from MyAppSubclass.application.parameters or in mxml Application.application.parameters.

For example I have a product ID I want to pass to a small swf when I load it.

<mx:Application 
	xmlns:mx="http://www.adobe.com/2006/mxml" 

	creationComplete="initVars()"

	 height="65">
    <mx:Script><![CDATA[
    	
        [Bindable]
        public var productId:String;
        
        // Assign values parameters to properties.
        private function initVars():void {
            productId = Application.application.parameters.productId;
        }
        
    ]]></mx:Script>
    
    <mx:VBox fontSize="18" fontFamily="Arial">
    <mx:HBox>
        <mx:Label text="Product Id: "/>
        <mx:Label text="{productId}" fontWeight="bold"/>
    </mx:HBox>
    </mx:VBox>
</mx:Application>

All I have to do is load the swf with a query string tacked on the end of the swf’s url and supply the key, value pair for my variable.

key: productId
value: 2983127

(or any other product id I need, be careful of invalid strings!)

so the swf load url would look something like…

myflex.swf?productId=2983127

The mxml will run straight from Flex Builder 3 so try it out for yourself and try loading the swf you compile into a browser (without HTML) and put ?productId=THX1138 on the end of the url. The productId will be shown in the SWF.

Naming conventions make programs more understandable by making them easier to read. They can also give information about the function of the identifier-for example, whether it’s a constant, package, or class-which can be helpful in understanding the code In a nutshell it’s about injecting as much meaning into your code as possible, while still remaining terse and concise. I could just suggest you meditate on the phrase, semantic richness.

Packages

The prefix of a unique package name is always written in all-lowercase ASCII letters and should be one of the top-level domain names, currently com, edu, gov, mil, net, org, or one of the English two-letter codes identifying countries as specified in ISO Standard 3166, 1981.

The second part of your top level package should be named after your organisation type, or the organisations name itself, eg. package name tv.simplymedia for simplymedia.tv. then your package begins to describe the code sections themselves, eg. app, view, controller, model etc..

example package names

com.mydomain.app
jp.co.domain.viewer.app
edu.mit.logger

Classes

Class names should be nouns, in mixed case with the first letter of each internal word capitalised. Try to keep your class names simple and descriptive. Use whole words-avoid acronyms and abbreviations, waive this rule if the abbreviation is much more widely used than the long form, such as URL or HTML, in these cases use the form Url, Html etc…

example class names

class Raster {...}
class ImageSprite {...}

Interfaces

Interface names should be capitalised like class names but given a “I” prefix. They should also describe the set of methods (behaviours) which they enforce.

example interface names

interface IDisplayable
interface IStoring

Methods

Methods should be verbs, in mixed case with the first letter lowercase, with the first letter of each internal word capitalized.

example method names

run();
runFast();
getBackground();

Variables

Except for variables, all instance, class, and class constants are in mixed case with a lowercase first letter, subsequent words start with capital letters. Variable names should not start with underscore _ or dollar sign $ characters, even though both are allowed. However private and protected class properties should be prefixed with _(underscore) if they are to be used with public get/set functions.

Variable names should be short yet meaningful. The choice of a variable name should be mnemonic- that is, designed to indicate to the casual observer the intent of its use. One-character variable names should be avoided except for temporary “throwaway” variables. Common names for temporary variables are i, j, k, m, and n for integers; c, d, and e for characters. However, avoid over use of these single letter vars for anything other than iterators.

i:int;
name:String;
baseWidth:Number;

private var _height:Number;

public function get height():Number {
    return _height;
}

public function set height(value:Number):void {
    _height = value;
}

Constants

The names of variables declared class constants should be all uppercase with words separated by underscores (“_”).

public static const MIN_WIDTH:Number = 4;
public static const MAX_WIDTH:Number = 999;