Entities outside SystemBase

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Is it possible to list the entities I need with components via ForEachLambdaJobDescription Entities without the SystemBase class?

Let's say there is some event that enumerates entities only once in a lifetime, and calling onUpdate SystemBase every time sounds somehow too cumbersome.

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Answer by andrew-lukasik · Apr 27 at 08:19 AM

Yes. You can query and grab whatever data you need, even from a common MonoBehaviour.

But be aware that everything Unity.Collections ( NativeArray<T> etc) will be slow to read/write outside a job. So still prefer jobs where possible (you can start them from Monobehaviours too)

 void Start ()
 {
     var world = World.DefaultGameObjectInjectionWorld;
     var entityManager = world.EntityManager;
 
     var query = entityManager.CreateEntityQuery(
         typeof(RenderBounds)
     );
     
     NativeArray<Entity> entities = query.ToEntityArray( Allocator.Temp );
     Entity[] entitiesArray = entities.ToArray();
     
     NativeArray<Entity> renderBounds = query.ToComponentDataArray<RenderBounds>( Allocator.Temp );
     RenderBounds[] renderBoundsArray = renderBounds.ToArray();
 }

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daliksn · Apr 28 at 10:17 AM 0

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Thanks. Is it possible to achieve the same syntax as in Entities through a lambda instruction? And is it also a good practice from a performance point of view to create multiple arrays at once through ToComponentDataArray in order to work with several components at once through enumeration, and not with one?

andrew-lukasik daliksn · Apr 28 at 11:08 AM 0

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Is it possible to achieve the same syntax as in Entities through a lambda instruction?

Seems like a busywork, but syntax-wise - I can't see why not.

is it also a good practice from a performance point of view to create multiple arrays at once through ToComponentDataArray in order to work with several components at once through enumeration, and not with one?

Allocation time is rarely an issue, but when it becomes one - you can always use ToComponentDataArrayAsync instead of ToComponentDataArray.

More important thing: if you want anything here to be fast, your best choice is to create Burst-compiled jobs and schedule that. Everything else is low-performance, in comparison.

Sidenote: you don't want to enumerate any NativeArray<T> in Start (it's super slow).

daliksn andrew-lukasik · Apr 28 at 11:10 AM 0

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Thanks, I'll remember.

Entities outside SystemBase

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