How to manage entity display data and logical data?

What's a good way to store an entity's display data and an entity's logical data? Entities need to go on seperate layers (so like, background objects go behind foreground or so that enemies are always displayed underneith of bullets, etc.). The problem is, how do you manage these lists?

Does this seem like a logical solution?

I have a World object. The World object stores a list of all entities. To create a new entity, you go world.createEntity(type) and when a new entity i开发者_如何转开发s created, the world fires an entityCreatedCallback function that notifies all of the listeners that a new entity was created. In my PlayGameState class, I attach a listener to the world to listen in and when a new entity is created, I add that entity to an appropriate display layer for drawing later.

Then during the game loop I cascade like this:

allScreens.update() -> world.update() -> allEntities.update()

allScreens.draw() -> playGameScreen.draw() -> allLayers.draw()

Does that seem reasonable?

You are talking about a 2D game, right?

I like your architecture, because it seperates the creation of the entities with their initialization and use. I think it is clean and extensible.

In a game I wrote I had a similar approach, but my rendering engine made it easy for me and supported DisplayGroups which automatically rendered the objects in the right order. I don't know what technology you are using, but generally speaking if you are using hardware rendering with OpenGL/DirectX you could use the Z values to achieve the effect (literally place background objects behind).

In case you use software rendering, I think there is no other option than to order the objects before you draw them on the surface.

HTH