Question Cleaning up Entities from MonoBehaviours

I am still quite new to ECS, I have managed to setup a basic stats system with it that works quite well for my needs, but now I seem to be having a problem calling DestroyEntity. I am creating and destroying my entities from MonoBehaviour "Manager" scripts. It works just fine in normal gameplay, but (often) throws a lot of quite nasty looking errors in the console once I exit play mode, and I'm worried that could be part of a much bigger problem. Here is my code and it is the destroy entity part (in OnDestroy) that is causing the problem.

Code (CSharp):

1. public class MonsterStatsManager : MonoBehaviour
2. {
3.     public MonsterStats Stats => entity.Index > 0 ? entityManager.GetComponentData<MonsterStats>(entity) : monsterStats;
4.  
5.     [SerializeField] MonsterStats monsterStats;
6.  
7.     Entity entity;
8.     static EntityManager entityManager;
9.     static EntityArchetype monsterArchetype;
10.  
11.     void Awake()
12.     {
13.         entityManager = entityManager == default(EntityManager) ? World.DefaultGameObjectInjectionWorld.EntityManager : entityManager;
14.         monsterArchetype = monsterArchetype == default(EntityArchetype) ? entityManager.CreateArchetype(typeof(MonsterStats), typeof(MonsterStatsDispatcher)) : monsterArchetype;
15.     }
16.  
17.     void Start()
18.     {
19.         entity = entityManager.CreateEntity(monsterArchetype);
20.         monsterStats.name = Regex.Replace(gameObject.name, @" ?\(.*?\)", string.Empty).Trim();
21.         entityManager.SetName(entity, $"MonsterStats ({gameObject.name})");
22.         entityManager.SetComponentData(entity, monsterStats);
23.     }
24.  
25.     void OnDestroy() => entityManager.DestroyEntity(entity);
26.  
27.     public void Dispatch<T>(T dispatch) where T : struct => StatsDispatchHelpers.Dispatch<T, MonsterStatsDispatcher>(dispatch, entity);
28. }

The error I am getting is this and sometimes multiple times, happens only when stopping play mode, and sometimes doesn't happen:

InvalidOperationException: The NativeArray has been deallocated, it is not allowed to access it

Unity.Collections.LowLevel.Unsafe.AtomicSafetyHandle.CheckWriteAndThrowNoEarlyOut (Unity.Collections.LowLevel.Unsafe.AtomicSafetyHandle handle) (at <2feaf16e80004e0cadae3f2e05f2a3fa>:0)

Unity.Collections.LowLevel.Unsafe.AtomicSafetyHandle.CheckWriteAndThrow (Unity.Collections.LowLevel.Unsafe.AtomicSafetyHandle handle) (at <2feaf16e80004e0cadae3f2e05f2a3fa>:0)

Unity.Entities.EntityManager.GetCheckedEntityDataAccess () (at Library/PackageCache/com.unity.entities@0.11.2-preview.1/Unity.Entities/EntityManager.cs:70)

Unity.Entities.EntityManager.DestroyEntityInternal (Unity.Entities.Entity* entities, System.Int32 count) (at Library/PackageCache/com.unity.entities@0.11.2-preview.1/Unity.Entities/EntityManagerCreateDestroyEntities.cs:341)

Unity.Entities.EntityManager.DestroyEntity (Unity.Entities.Entity entity) (at Library/PackageCache/com.unity.entities@0.11.2-preview.1/Unity.Entities/EntityManagerCreateDestroyEntities.cs:172)

PlayerStatsManager.OnDestroy () (at Assets/Scripts/Stats/PlayerStatsManager.cs:34

 

Think I figured out this one myself, it was my cached EntityManager that was causing the problem, I reworked it a bit to check if the world was null (and also read EntityManager directly from World.DefaultGameObjectInjectionWorld).

Code (CSharp):

1. public class MonsterStatsManager : MonoBehaviour
2. {
3.     public MonsterStats Stats => entity.Index > 0 ? World.EntityManager.GetComponentData<MonsterStats>(entity) : monsterStats;
4.  
5.     [SerializeField] MonsterStats monsterStats;
6.  
7.     Entity entity;
8.     static World World => World.DefaultGameObjectInjectionWorld;
9.     static EntityArchetype monsterArchetype;
10.  
11.     void Awake()
12.     {
13.         monsterArchetype = monsterArchetype == default(EntityArchetype) ? World.EntityManager.CreateArchetype(typeof(MonsterStats), typeof(MonsterStatsDispatcher)) : monsterArchetype;
14.     }
15.  
16.     void Start()
17.     {
18.         EntityManager entityManager = World.EntityManager;
19.         entity = entityManager.CreateEntity(monsterArchetype);
20.         monsterStats.name = Regex.Replace(gameObject.name, @" ?\(.*?\)", string.Empty).Trim();
21.         entityManager.SetName(entity, $"MonsterStats ({gameObject.name})");
22.         entityManager.SetComponentData(entity, monsterStats);
23.     }
24.  
25.     void OnDestroy() => World?.EntityManager.DestroyEntity(entity);
26.  
27.     public void Dispatch<T>(T dispatch) where T : struct => StatsDispatchHelpers.Dispatch<T, MonsterStatsDispatcher>(dispatch, entity);
28. }