Slick Forums

I've got a portion of my system where a lot of entities share one aspect (health), but diverge on other things (such as: some have shields, some are bullets, some have temporary life, etc.) I've been using group tags to determine what kind of group an entity belongs in so I can take appropriate action. For example, when I have bodies collide in the physics engine, I need to determine if the related entity has shields or not, and then apply damage to that or directly to health if shields are not present.

In looking at this, I am wondering about the efficiency of using a tag versus defining an "EntityGroup"-style component that would retrieve this type of information for these entities. What's the benefit of using a tag versus using a component? I think these will accomplish the same thing, but I get the feeling the component approach will induce less overhead.

Thanks,
--tim

You can implement tags using component and a system, no problem.

I have been using an entity system I built myself that is very similar to Artemis. I included a method on Entity named HasComponent(), that allows a system to query an entity to see if it has a component of a specific type. In this manner, you could them have your system process all entities with a Health component, and then query each to see if it had a Sheilds component, in this way you wouldn't need a tag at all.

I guess the one disadvantage to this approach is that you lose the ability to collectively retrieve a group. I have a mini-radar HUD system that gets all objects that are part of the barrier group (asteroids, etc.). If I go with a component that's a "BodyType", then I can't retrieve just the types that are barriers, or the types that are just bonus pickups.

--tim

Artemis has something similar. If you use a component mapper, for example, you can call componentMapper.getSafe(entity). This will return a null if the entity does not have the related component.

For now, I've decided against using a component for body type. I'll revisit this in the future if I run into performance issues.

Cheers,
--tim