Best way to spawn many prefabs and have them reference each other in components

I have Unit which spawns these prefab Entities: a single Officer, a single Formation, and many Soldiers. Officers, Formations, and Soldiers need to reference each other in their components. However, this can quickly become extremely complicated since instantiated Entities have negative indices right after creation, and should not be stored in components until the ECB has played back and converted the negative indices to positive ones. Are there any good patterns for creating and linking these spawned entities?

 

Using ECB Add/Set component works correctly with the negative entity indices. ECB remaps them during playback.

 

Small additional note:
Only if add/set processed in the same ECB where temp entity index was created.

 

Correct, though you might only be referring to this case

Code (CSharp):

1. var created = ecb.Instantiate(prefab);
2.  
3. ecb.SetComponent(created, new SomeComponent());

I am wondering about this case

Code (CSharp):

1. var created = ecb.Instantiate(prefab);
2.  
3. ecb.SetComponent(existing, new OtherComponent { entity = created });

Is the ECB smart enough to remap the entity correctly in the second case?

 

Yes

 

Thanks. Last question is regarding the whole "same ECB" requirement. If I do

Code (CSharp):

1. var created = ecb.Instantiate(prefab);
2. ecb.SetComponent(existing, new OtherComponent { entity = created });

and the negative Entity stays in OtherComponent for several frames, which means the original ECB has disappeared, then what happens when a new ECB several frames later tries to do something like

Code (CSharp):

1. var otherComponent = GetComponent<OtherComponent>(existing);
2.  
3. var previouslyCreated = otherComponent.entity;
4.  
5. ecb.SetComponent(previouslyCreated, new AnotherComponent());

where previouslyCreated is still a negative Entity. Basically, do I never have to worry about negative Entities?

 

Also, could I use GetComponent on newly instantiated entities?

 

That should be impossible. SetComponent has to be played back from the ECB. And when it does, it will remap the entity. When you call GetComponent, you either get the value of the component before ECB.SetComponent, or after ECB.Playback in which case the value is already remapped. The only way I could see this failing is if you create and destroy the same entity in the same ECB. I'm not sure if that is possible to do, but if it is, it is stupid, so don't do it.

 

Not before the ECB that instantiated the entity is played back