How to enforce derived classes to implement methods in AS3? - actionscript-3

Question

I have a rather simple theoretical question regarding OOP (in AS3) that I don't know how to google:
I need something like an abstract class, which would require that dependant class implements some interface, like this:
Interface ISomething
{
public function somethingize(otherThing:type):void;
}
abstract public class AbstractSomething implements ISomething
{
public function AbstractSomething()
{
// ...
}
public function doSomething():void
{
//code here
// ...
this.somethingize();
// ...
}
}
Is the only way to achieve such a thing is to drop an "abstract" keyword, and move somethingize to SomethingWrapper (with an implementation of throwing an "unimplemented exception"), or is there some better way to model it?

Answer 1

ActionScript doesnt support Abstract classes (unfortunately).
I think there are a few techniques out there to try and mimic abstracts, but my way is too just throw errors in my abstract classes to stop them being used directly, eg:
public class AbstractSomething implements ISomething
{
public function AbstractSomething()
{
throw new Error("this is an abstract class. override constructor in subclass");
}
public function doSomething():void
{
throw new Error("this is an abstract class. override doSomething in subclass");
}
}

Answer 2

Without more information about the specific implementation, I would prefer composition over inheritance in this case, specifically dependency injection.
public interface ISomething {
function somethingize(thing:*):void;
}
public class SomeWorker {
private var _something:ISomething;
public function SomeWorker(something:ISomething) {
this._something = something;
}
public function doSomething():void {
// work
this._something.somethingize(obj);
// more work
}
}
Inherrited classes of SomeWorker could inject the correct implementation of ISomething for the work they need to do, or that dependency could be resolved somewhere else.