Comments on: Get the class used to create an object instance in AS3

By: websites accesed so far to help understand ActionScript 3 « Dave Potts Blog

websites accesed so far to help understand ActionScript 3 « Dave Potts Blog — Wed, 10 Feb 2010 20:11:24 +0000

[...] Get the class used to create an object instance in AS3 – Josh Talks Flash [...]

By: intense creativity » SWF TextField Factory — Dynamically Loading Fonts in AS3

Fri, 11 Dec 2009 05:05:56 +0000

[...] like the FontAsset class.. how do I get a pure Font class? After some researching, I find this post which describes the "constructor" property of all objects.. cool. This will let you simulate [...]

By: jeff

jeff — Fri, 05 Jun 2009 20:51:58 +0000

Sweet, thanks. I have been wondering how to do that for a little while now.

By: Josh Tynjala

Josh Tynjala — Fri, 05 Jun 2009 18:14:41 +0000

There is no way to get the object that called a function, unless you require that it gets explicitly passed in. Something like this would work:

public function setExample(exampleValue:Object, caller:SpecialType):void
{
    if(caller == null)
    {
        throw new Error("Caller must be of type SpecialType.");
    }
    this._example = exampleValue;
}

Personally, I don't like that approach. A better one might be to use namespaces. You can define the same namespace separately in each class:

private namespace only_special_type = "http://www.example.com/only_special_type";

...and then use it instead of public for your setter:

only_special_type function set example(value:Object):void
{
    this._example = value;
}

That won't stop people from using your setter if they know how to define the same namespace, but they'll have to explicitly make that choice, so it adds a stronger barrier to entry.

By: jeff

jeff — Fri, 05 Jun 2009 17:46:25 +0000

Would there be a way, using this method, to determine in a setter function what class was trying to set the value in another class?

So if a variable was only supposed to be able to be set from a specific class, others would error out?

By: Justin Reidy

Justin Reidy — Wed, 13 May 2009 12:06:00 +0000

I was just about to ask about the relative speeds – should have known you’d check, Ben!

This is great stuff, Josh. Thanks for the post.

By: Ben Clinkinbeard

Ben Clinkinbeard — Tue, 12 May 2009 14:16:04 +0000

Nice find Josh, I wasn’t familiar with this approach. Not only does it look cleaner in my opinion but based on some rudimentary testing it appears to be about 4 times faster as well.

By: Roland Zwaga

Roland Zwaga — Tue, 12 May 2009 08:03:17 +0000

The as3-commons projects came forth out of Spring Actionscript and offers quite an extensive reflection library, you might like to check it out here: AS3 Commons Reflect

By: Campbell

Campbell — Mon, 11 May 2009 21:08:27 +0000

I have wrapped the flash.utils methods in a Util class that caches the object definitions… seeing Class definitions are static, it works out pretty well. That way I can cache all sorts of metadata etc on the classes.

This is the first time I have really seen any use for the constructor property though well done

If I find time ill clean it up and post a link