deep clone entity components

ContextExtensions.CloneEntity creates entity with shallow copied components

    public static TEntity CloneEntity<TEntity>(this IContext<TEntity> context, IEntity entity, bool replaceExisting = false, params int[] indices) where TEntity : class, IEntity
    {
      TEntity entity1 = context.CreateEntity();
      entity.CopyTo((IEntity) entity1, replaceExisting, indices);
      return entity1;
    }

I’m using prototype entities, which are cloned at runtime. So far I stored behaviour classes with readonly data inside component fields, so shallow copying kinda worked. But recently added BehaviourTreeComponent for AI and it needs to store some data.

What could be a solution to get entity deep clone? Or can I get out with storing POD components?

[sschmid]

Hi, 2 thoughts, one on deep copy and one on an alternative solution for your problem:

1. Deep Copy A generic solution for deep copying is probably not a good idea. Deep cloning a component with complex objects is probably way more complicated and more overhead compared to simply construct new objects manually. Deep copying can make sense if you know what objects you are dealing with, but I wouldn’t strive for a general solution. Objects might have references to other objects that have to be cloned that have references to objects that have to be cloned that have other ref… and so on, which leads me to:

2. Configuration / Entity Factory If I understand correctly you basically trying to create some template / blueprint entities that you will clone at runtime. If you break it down, this is basically configuration. I worked on many games with lots of external configuration. Configs are simple first and can grow in complexity. Chances are that game designers and level designer will take over the responsibility to maintain configurations. I recommend having tools for working with configs like google sheets, custom Unity inspectors or sth like that which output a versioned config in structure independent from your game architecture, e.g. Text formats like JSON or binary formats like Flax Buffers / protobuf or similar.

We created a class, e.g. CharacterSetupService, BuildingSetupService that know how to construct entities based on the configuration, e.g.

public virtual GameEntity CreateCharacter(Contexts contexts, string id, string type, Gender gender, int positionX, int positionY, string state) {
    var e = contexts.core.CreateEntity();

    // Add components every character needs
    SetupEntitySpecificComponents(e, id, type, gender, positionX, positionY, state);

    // Add components based on config
    AddComponentsFromConfig(contexts, e);
    return e;
}

var character = characterSetupService.CreateCharacter(contexts, id, type, gender, 0, 0, CharacterState.Idle);

This approach also allows you to simply write unit tests because you can mock the CharacterSetupService and have config independent tests

[sschmid]

I see too many cases where deep copying doesn’t make sense and therefore can’t be included in Entitas as a general solution. If you have specific cases where you need it, you have to implement it yourself, which I think would be the better way anyway as you have oversight on what objects you actually plan to deep copy.