Mechanism to elegantly cleanup components

Use case:

PhysicsComponent contains a Box2D body. Every time either a component of this class is removed from an entity or the entity itself is removed from the engine, we need to call world.destroyBody(component.body). It would be nice to have a mechanism to catch this event and act accordingly.

Options:

• EntityListener that processes entities in the family of entities with physics component that does the cleanup on entity removed from the family.
• Make ComponentListener a public class and have something like this:

public interface ComponentListener {
    public void componentAdded(Entity e, Component e);
    public void componentRemoved(Entity e, Component e);
}

public class Engine {
    public void addComponentListener(Class<? implements Component> componentClass, ComponentListener listener)
    public void removeComponentListener(Class<? implements Component> componentClass, ComponentListener listener);
}

• Somehow reuse the Entity signaling system that already notifies engine of these events.
• Component could implement Disposable and the Engine would call dispose() if it implements the interface. Nasty because it adds logic to components.

What do you guys think would be best?

[mgsx-dev]

I would go for solution 2 for many reasons :

• it address both component cleanup and component initialization. With the Box2D example, you may want to create body once component added. With this solution, both body creation/destruction code would be in the same listener.
• sometimes you need whole entity to cleanup/initialize component which is not possible with the dispose method.

For now my workaround is to use PooledEngine and implements Poolable interface on my components which works but it doesn’t work with other engine implementation.

@saltares I think this topic should be reopened.

[tdgroot]

Since nothing really happened on this issue, I’ll just drop my solution here: https://gist.github.com/Desmaster/a05d669208a05f98e8074761af5aad98

Could be way more advanced, but it currently fits my needs.