Create Component with referenced Entity

Hi,

I've the following situation:

I need to create an Entity and hold the entity in an EntityReference Component of an other entity.
Now this is done in one step.

Problem is I can't use PostUpdateCommand to create the entity because I won't get an Entity back.
So I created an EntityFactoryWorld with its own EntityManager.
And at some point I move my entities from the EntityFactoryWorld to my normal world

But what happens with the Entity in the EntityReferenceComponent?
As I imagine, I won't be able to find the entity anymore?

How to solve this problem?

Code (CSharp):

1. struct EntityReference : IComponentData {
2.       public Entity value;
3. }
4.  
5. //...
6. void Foo() {
7.      Entity otherEntity = EntityFactory.CreateSomeEntity();
8.      PostUpdateCommand.AddComponent(entities[i], new EntityReference { value = otherEntity });
9. }
10.  
11.  

 

PostUpdateCommand is good to defer the command to post update. If you need instant access the values you can always use EntityManager.CreateEntity.

 

Well, but this will create a hard sync point.

 

Well yeah, that is one of the side effect. One way to reduce the effect is pushing the system to the very end of the frame:

using UnityEngine.Experimental.PlayerLoop;

[UpdateAfter (typeof (PostLateUpdate))]

 

Well that's not a solution for me :/

It would invalidate my current system... (need to create entity with ComponentType.FixedArray)
One more thing is that this doesn't work well on a more complex scenario...

 

Sync points are to be expected I guess. Just not too many of them in one frame. I did just end up using EntityManager.CreateEntity. It's quite performant. I could spawn like 10,000 entities on the main thread in around 100ms. Of course this doesn't happen every frame.

 

you could do a 2-steps thing:

Code (CSharp):

1. public class InverseEntityReference : IComponentData {Entity value;}
2.  
3. // step 1: create entity
4. PostUpdateCommands.CreateEntity(archetype);
5. PostUpdateCommends.AddComponent(new InverseEntityReference {value = oldEntity});
6.  
7. //step 2: invert references system
8. struct Group {
9.     public ComponentDataArray<InverseEntityReference> references;
10.     public EntityArray entities;
11. }
12. OnUpdate loop: {
13.     PostUpdateCommands.AddComponent (group.references[i].value, new EntityReference{value = group.entities[i]});
14.     PostUpdateCommands.RemoveComponent<InverseEntityReference>(group.entities[i])
15. }

 

Hi, thank you for the answer! I made it the way you described it.
I've used 2 systems one for creating the entity and another that runs after the first one to assign the correct relations.