preloader absorbing application FlashVars

As has happened frequently, after completing a Flash application, I find that the size of the application demands a preloader swf to load the application swf (complete with progress bar). the problem i have found with this preloader swf is that it now absorbs any FlashVars that the application swf was expecting to be passed to it from the html.

how to get the preloader to pass the FlashVars to the application? well, the preloader could extract the FlashVars and explicitly send them to the application in a function call once the application is loaded. but this would mean that the application would work differently than it would have prior to the loader. it could also mean that the preloader may have to be modified for each project, whereas a generic preloader would be much simpler.

here is a solution that means the application works exactly the same, and the preloader can remain generic – within the preloader extract all the FlashVars, and pass them along to the application as URLVariables in the URLRequest.data property.

[sourcecode language=”actionscript3″]
var ldr:Loader = new Loader();
var url:String = “application.swf”;
var urlReq:URLRequest = new URLRequest(url);
urlReq.data=getObjectURLVariables(this.loaderInfo.parameters)
ldr.load(urlReq);
this.addChild(ldr);

public function getObjectURLVariables(whichObject:Object):URLVariables {
var variables:URLVariables=new URLVariables();
for (var i in whichObject) {
variables[i]=whichObject[i];
}
return(variables);
}
[/sourcecode]

You could quite easily set this up as a custom Loader class that automatically passes the FlashVars along to the loaded application.