Iterating over Entities in jobs

Hello,
Help me please to understant how can I convert ComponentSystem to JobComponentSystem.
Problem is that I can't understand how I can iterate over all Entities with required Component inside job.

Here is code on Component System - it works

Code (CSharp):

1. public class FindTargetForZombieSystem : ComponentSystem {
2.     protected override void OnUpdate() {
3.         Entities.WithAll<Zombie>().WithNone<Target>().ForEach((Entity entity, ref Translation translation) => {
4.             Entities.WithAll<Human>().ForEach((Entity targetEntity, ref Translation targetTranslation, ref HealthData healthData) => {
5.                // ... some code
6.         });
7.     }
8. }

And this is my attempt of converting it to JobComponentSystem

Code (CSharp):

1. public class FindTargetForZombieSystem : JobComponentSystem {
2.     private EntityCommandBufferSystem _bufferSystem;
3.  
4.     protected override void OnCreate() {
5.         _bufferSystem = World.GetExistingSystem<EndSimulationEntityCommandBufferSystem>();
6.     }
7.    
8.     [ExcludeComponent(typeof(Target))]
9.     [RequireComponentTag(typeof(Zombie))]
10.     [BurstCompile]
11.     public struct FindTargetJob : IJobForEach<Translation> {
12.         public EntityCommandBuffer.Concurrent CommandBuffer;
13.  
14.         public void Execute(ref Translation translation) {
15.            // How can I iterate over all Entities with "Human" component here ?
16.         }
17.     }
18.    
19.     protected override JobHandle OnUpdate(JobHandle inputDeps) {
20.         var jobHandle = new FindTargetJob {
21.             CommandBuffer = _bufferSystem.CreateCommandBuffer().ToConcurrent()
22.         }.Schedule(this, inputDeps);
23.         _bufferSystem.AddJobHandleForProducer(jobHandle);
24.         return jobHandle;
25.     }
26. }

So how can i get entities with "Human" inside job ?

 

First of all - use SystemBase as (Job)ComponentSystem will be removed eventially. IJobForEach deprecated already and will be removed. You should use Entities.ForEach from SystemBase where Unity improved codegen in comparison with previous versions in (Job)ComponentSystem.

 

Thank you

But nested Entities.ForEach Lambda expressions are not supported in SystemBase - what is the best way to do it ?

 

Supported. You just should use WithoutBurst() and Run() to make it mainthreaded and not burst compiled.

 

There was a similar thread here: https://forum.unity.com/threads/systembase-and-multiple-foreach.875002/#post-5757646

 

Thank for that link. Looks like my target system is same, but In runtime I have this error

ArgumentException: The previously scheduled job FindTargetForZombieSystem:<>c__DisplayClass_OnUpdate_LambdaJob0 writes to the NativeArray <>c__DisplayClass_OnUpdate_LambdaJob0.JobData.ecb. You must call JobHandle.Complete() on the job FindTargetForZombieSystem:<>c__DisplayClass_OnUpdate_LambdaJob0, before you can write to the NativeArray safely.

EntityCommandBuffer was recorded in FindTargetForZombieSystem and played back in Unity.Entities.EndSimulationEntityCommandBufferSystem.

This happends after trying to add component to EnityBuffer. What wrong with that ?

Code (CSharp):

1. protected override void OnCreate() {
2.         _ecbSystem = World.GetOrCreateSystem<EndSimulationEntityCommandBufferSystem>();
3.         _humansQuery = GetEntityQuery(
4.             ComponentType.ReadOnly<Human>(),
5.             ComponentType.ReadOnly<Translation>());
6.     }
7.    
8.     protected override void OnUpdate() {
9.         var ecb = _ecbSystem.CreateCommandBuffer().ToConcurrent();
10.        
11.         var translationType = GetArchetypeChunkComponentType<Translation>();
12.         var entityType = GetArchetypeChunkEntityType();
13.         var chunks = _humansQuery.CreateArchetypeChunkArray(Allocator.TempJob);
14.        
15.         Entities
16.             .WithReadOnly(translationType)
17.             .WithReadOnly(entityType)
18.             .WithDeallocateOnJobCompletion(chunks)
19.             .WithAll<Zombie>()
20.             .WithNone<Target>()
21.             .ForEach((Entity entity, int entityInQueryIndex, in Translation translation) => {
22.                 var position = translation.Value;
23.                 var closestTarget = Entity.Null;
24.                 var closestDistance = float.MaxValue;
25.  
26.                 for (var chunkIndex = 0; chunkIndex < chunks.Length; chunkIndex++) {
27.                     var chunk = chunks[chunkIndex];
28.                     var chunkEntities = chunk.GetNativeArray(entityType);
29.                     var translations = chunk.GetNativeArray(translationType);
30.  
31.                     for (var i = 0; i < chunk.Count; i++) {
32.                         var target = chunkEntities[i];
33.                         var targetTranslation = translations[i];
34.                         var distanceToTarget = math.distance(position, targetTranslation.Value);
35.  
36.                         if (closestTarget == Entity.Null || distanceToTarget < closestDistance) {
37.                             closestTarget = target;
38.                             closestDistance = distanceToTarget;
39.                         }
40.                     }
41.                 }
42.                
43.                 if (closestTarget != Entity.Null) {
44.                     ecb.AddComponent(entityInQueryIndex, entity, new Target {
45.                         Entity = closestTarget
46.                     });
47.                 }
48.             }).ScheduleParallel();
49.     }

 

Add

Code (CSharp):

1. _ecbSystem.AddJobHandleForProducer(Dependency);

at the end of OnUpdate().