Loading external swf and assign it to custom class

Question

I have a BuildingSprite that extend Sprite. I try to load external swf library into my main application.

I have this code and it works fine:

private function loadBuilding():void{
// this context is necessary to find the shared assets
var context:LoaderContext = new LoaderContext(false, ApplicationDomain.currentDomain);

// load in the asset swf
var loader:Loader = new Loader();
var req:URLRequest = new URLRequest("assets/Tree.swf");
loader.contentLoaderInfo.addEventListener(Event.COMPLETE, onAssetsLoaded);  
    loader.load(req, context);
 }


private function onAssetsLoaded(_event:Event):void{
// get a reference to the loaded library
var loader:Loader = LoaderInfo(_event.target).loader;
var library:* = loader.content;
var assetClass:Class = loader.contentLoaderInfo.applicationDomain.getDefinition("Tree") as Class;
// create an instance of the shared asset
var mySprite:Sprite = new assetClass();       
.....
 }

I created a new class - BuildingSprite that extends Sprite:

    package
{   
import flash.display.Sprite;

public class BuildingSprite extends Sprite
{
    public function BuildingSprite()
    {
        super();
    }
}
}

And from the onAssetsLoaded above, I change the code:

var mySprite:Sprite = new assetClass();

to

var mySprite:BuildingSprite = new assetClass();

I debug and get this error: Main Thread (Suspended: TypeError: Error #1034: Type Coercion failed: cannot convert Tree@c8f0301 to BuildingSprite.)

I think there is a type casting error. Is there any way to load the external swf library and assign it to custom class?

Daniel · Accepted Answer · 2011-01-21 18:46:44Z

the problem here is that Tree is a class extending the Sprite class already "cannot convert Tree@c8f0301"

BuildingSprite is another class extending sprite. Think of it as a tree where Sprite is the trunk, and the classes are the branches, while both relate to their original Sprite class, they don't recognize each other.

what you'd need to do is show how they are related. by converting the Tree to sprite and the sprite to BuildingSprite in two steps.

var mySprite:BuildingSprite = (new assetClass() as Sprite) as BuildingSprite ;

If you have extended the Sprite class with additional functions in your Tree class, you would loose those functions or get into some issues, but if it is just a graphic that you want to use, this should do it.

on a side note, using available libraries can speed things up. So if you get a chance, do have a look up the casalib, specifically (pertaining to the topic) the contentAsMovieClip and createClassByName functions under swfLoad

edit

Looks like I should have tested it more. It turns out that that if you do this var s:Sprite = (new assetClass() as Sprite), it converts s to whatever class assetClass() is rather than the other way around, so if you do a trace of s it won't be a Sprite any more

the way I deal with this is create a generic sprite (actually CasaSprite) and add a var view:Sprite (or displayObject or MovieClip) as a child. This is probably not the answer that you were looking for, but it works.

billy_flow · Accepted Answer · 2011-01-21 08:18:25Z

I tried to trace the code:

trace(new assetClass() as Sprite)

And it returned:

[object Tree]

And

trace( (new assetClass() as Sprite) as BuildingSprite )

But it returned:

null

I created the the Tree.swf with a Tree symbol in the Library that

enable "Export for ActionScript"
and "Base Class : flash.display.MovieClip"

Any error here?

Thanks for guide. I am creating a game using an isometric library. Instead of loading each building with png using BitmapData, I try to load an external library swf that contains all the buildings in the library.

I believe the file size for the swf will smaller than all the png files. I need a custom class for Building that extends Sprite/MovieClip so that I can have custom properties like Direction, Cost, etc. Do you have any resource sample code that I can download for reference? Thanks.

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