Question How to get data from a burst job execution

Hello. I'm trying to make some tests on DOTS/ECS/... to get my head around it. Upon searching I'm coming across deprecated tutorials and answers or no answer at all.

I'm trying to make a prototype of a tycoon game in which I spawn a bunch of money producers (entities) and each producer keeps adding to a global total value (through a system). I could make a system in which every entity has it's own data and keep updating it, but there is another thing I need to do.

I need to update the global money for each entity that has a moneyProducer component. I also want to discuss on the available and best ways(performant) to do it.

PS: I've confirmed that the job is executing and adding to it's internal variables but I can't read it from the correct instance (or equivalent).

What I've tried so far:
• Scheduling or Running the job, then reading the value from it like

job.value

The value is always default, even after job execution.
• Handing the variable to the struct by reference.
Can't do that.
• Making an interface so the Job can send me a result.
Can't do that either.
• I've tried every single option of executing and completing the code I could get my hands on. To no avail.

Things I'm still thinking about
• I could try to have a component just to keep the global money and send it to the job, that's quite obvious. I don't know if that's the right approach on data oriented.
• Some time ago I've read/watched of having global public fields on ECS. Is this accomplished by components? (look like).

The system:

Code (CSharp):

1.  
2. using UnityEngine;
3. using Unity.Entities;
4. using Unity.Burst;
5. using Unity.Collections;
6. using Unity.Burst.Intrinsics;
7. using Unity.Jobs;
8.  
9. public partial class MoneyProduceSystem : SystemBase
10. {
11.     private EntityQuery query;
12.  
13.     public float moneyTotal = 0f;
14.  
15.     protected override void OnCreate()
16.     {
17.         this.query = GetEntityQuery(typeof(ProducerMoney));
18.     }
19.  
20.     protected override void OnUpdate()
21.     {
22.         this.query = GetEntityQuery(typeof(ProducerMoney));
23.         //Debug.Log("Scheduling job");
24.         UpdateMoneyJob jobMoney = new UpdateMoneyJob()
25.         {
26.             money =  moneyTotal,
27.             deltaTime = SystemAPI.Time.DeltaTime,
28.             producerType = GetComponentTypeHandle<ProducerMoney>()
29.         };
30.         //this.Dependency = jobMoney.ScheduleParallel(this.query, this.Dependency);
31.         //this.Dependency.Complete();
32.  
33.         //jobMoney.Run(this.query);
34.  
35.         JobHandle handle = jobMoney.ScheduleParallel(this.query, this.Dependency);
36.         handle.Complete();
37.        
38.  
39.         Debug.Log($"returned money {jobMoney.money} completed? {handle.IsCompleted}");
40.         moneyTotal = jobMoney.money;
41.     }
42.  
43.     [BurstCompile]
44.     public partial struct UpdateMoneyJob : IJobChunk
45.     {
46.         public float money;
47.         public float deltaTime;
48.         [ReadOnly]
49.         public ComponentTypeHandle<ProducerMoney> producerType;
50.  
51.         public void Execute(in ArchetypeChunk chunk, int unfilteredChunkIndex, bool useEnabledMask, in v128 chunkEnabledMask)
52.         {
53.             NativeArray<ProducerMoney> producers = chunk.GetNativeArray(ref this.producerType);
54.  
55.             for (int i = 0; i < chunk.Count; ++i)
56.             {
57.                 //ProducerMoney producer = producers[i];
58.  
59.                 this.money += producers[i].moneyProduced;
60.             }
61.             Debug.Log($"Money {this.money}");
62.         }
63.     }
64. }
65.  

The component:

Code (CSharp):

1. using Unity.Entities;
2.  
3. public struct ProducerMoney : IComponentData
4. {
5.     public float moneyProduced;
6. }

 

Found out that it works if I

Code (CSharp):

1.         float tempMoney = 0;
2.         this.Entities.ForEach((in ProducerMoney producer) => {
3.             tempMoney += producer.moneyProduced;
4.         }).Run();
5.         Debug.Log($"Money produced {tempMoney}");

After reading this doc (https://coffeebraingames.wordpress.com/2022/03/27/why-job-structs-are-better-than-entities-foreach/) about how much greater struct jobs are I didn't expect my old foreach to be the solution.
Is there any way to make it with the original structure?

 

NativeReference

 

Your job doesn't work because Job structs are copied before being scheduled. The reason updating NativeArrays from within a job works is because NativeArrays only store pointers to an outside buffer and don't contain the data directly.