AS3 game element structure - actionscript-3

Question

I'm trying to figure out how best to setup a kind of universal game element class for my game. What I want to try and create is a structure similar too..
GameElementPositionMovement (root class)
->GameElementVisual (handles all the graphics)
->GameElementPersonality (handles game logic)
I then want to be able to set up different personalities (monster, hero, icon etc) just by creating an instance of GameElementPersonality, but in it's constructor also be able to setup the visual and positioning/movement aspects as well.
I mentioned this in another question, and the answer that came back was...
It seems that you need kind of 'data model' class to store logic and a
visual ('view') class. Visual class shouldn't inherit from data model,
it should use it. This is OOP related problem: IS vs HAS (inheritance
vs composition)
But I'm not sure if I understand that. The position/movement without any visual data, seems a good first root class, and then you add to that the visual aspects (GameElementVisual), and then finally you add in personality "traits" (GameElementPersonality) such as armour, damage, health etc
Therefore I'm keeping, the positioning/movement, visual and logic separate, and I presumed the heirachy that I've laid out would be the best way to do that, but is this not a good way to do this? should it be more flat? with the GameElementPositionMovement, creating both a visual and logic instance and storing that in itself?

Answer 1

You could create a structure similar to this:
(pseudocode)
ElementData
//it doesn't have to extend any particular class
//however it would be nice if it could dispatch events and register listeners
class ElementData implements IEventDispatcher
{
public function ElementData() //constructor
{
//do some stuff
}
public function setSomeProperty(value:int):void
{
//
}
public function doSomeCrazyStuff():void
{
//
}
}
ElementVisual
class ElementVisual extends MovieClip //or just Sprite or even DiplayObjectContainer
{
public function ElementVisual(elementData)
{
//constructor takes an instance of ElementData class
elementData.addEventListener(CHANGE, onDataChange)
elementData.doSomeCrazyStuff();
if (userCliked)
{
elementData.setSomeProperty(15);
}
//you can have here some interactions with user (keyboard, mouse)
//then it can communicate with elenemtData and 'listen' what it says.
}
function onDataChange
{
//react accordingly
}
}
some visual representation (you may need many of these)
class Monster extends ElementVisual
{
//do all the graphic, animations etc
}
Then you need a class to set up all the data, visuals etc… In simplest implementation it can be the 'document class'.
It's not a proper MVC model - it's a simple example to show the concept of decoupling logic from visualisation.
MVC is not the only solution, there are other so called 'design patterns' which may be useful...

Answer 2

Yeah the idea with MVC is to keep things decoupled, in your case you're ultimately smashing everything into one chain of inheritance where you'll end up with one type of object that inherits all the properties from another object that inherits all the properties from another object, so you'll have an instance of this thing that represents everything, which is why this isn't a great pattern to go with.
If instead you have a GameElementPositionMovement class (Your main class) create an instance of the GameElementVisual and in instance of GameElementPersonality (or multiple instances if need be). Then any time a change to a property is made in GameElementPersonality (or any in the collection if you choose to make a collection) could dispatch an event, the main class GameElementPositionMovement could listen for the dispatched event and when it gets it can set/pass the GameElementPersonality instance or array to the GameElementVisual. Then in the GameElementVisual you're just dealing with drawing based on the current model all the time, the model is separated from the view logic, you'd also probably want to handle control in a separate class or in GameElementPositionMovement. (control being the modification of the model, in this case it would probably also be where you register listeners for user events, keyboard, mouse whatever)
This way the model remains clean of control logic and view logic, it's a clear separation of what goes where and really only the view sort of depends on the model and the controller sort of depends on the view but if interfaces are established for what the model view controller each need to communicate with each other in this way you can swap out any of those parts with a new class that implements the interface (not likely an issue in a small game, but the design lends itself to this ability and therefor future scalability).