Shutdown ECS/Scene switching

I want to switch to a non-ECS scene, i.e Main Menu. Every time I try to clean things up, I get a ton of errors.

This is what I have so far

Code (CSharp):

1.     private void OnDestroy()
2.     {
3.         if (_blobStore != null) {
4.             _blobStore.Dispose();
5.         }
6.  
7.         _entityManager.DestroyEntity(_entityManager.UniversalQuery);
8.         _world.DestroyAllSystemsAndLogException();
9.         _world.Dispose();
10.  
11.         _gameObjectSettings = null;
12.         _world = null;
13.     }

I've tried various combinations, but I still receive multiple errors:

ArgumentException: The World has already been Disposed.
Unity.Entities.World.Dispose () (at Library/PackageCache/com.unity.entities@0.10.0-preview.6/Unity.Entities/World.cs:268)
Startup.OnDestroy () (at Assets/Source/Startup.cs:58)​

InvalidOperationException: object is not initialized or has already been destroyed
Unity.Entities.ComponentSystemBase.CheckedState () (at Library/PackageCache/com.unity.entities@0.10.0-preview.6/Unity.Entities/ComponentSystemBase.cs:331)
Unity.Entities.ComponentSystem.Update () (at Library/PackageCache/com.unity.entities@0.10.0-preview.6/Unity.Entities/ComponentSystem.cs:86)
Unity.Entities.ScriptBehaviourUpdateOrder+DummyDelegateWrapper.TriggerUpdate () (at Library/PackageCache/com.unity.entities@0.10.0-preview.6/Unity.Entities/ScriptBehaviourUpdateOrder.cs:196)​

Before, I only had the blob asset dispose. Everything was fine. Now If I only dispose of the blob asset reference I get this error:

InvalidOperationException: The BlobAssetReference is not valid. Likely it has already been unloaded or released.
Unity.Entities.BlobAssetReferenceData.ValidateNonBurst () (at Library/PackageCache/com.unity.entities@0.10.0-preview.6/Unity.Entities/Blobs.cs:212)
Unity.Entities.BlobAssetReferenceData.ValidateNotNull () (at Library/PackageCache/com.unity.entities@0.10.0-preview.6/Unity.Entities/Blobs.cs:228)
Unity.Entities.BlobAssetReference`1[T].get_Value () (at Library/PackageCache/com.unity.entities@0.10.0-preview.6/Unity.Entities/Blobs.cs:309)
Unity.Physics.Broadphase+PrepareDynamicBodyDataJob.ExecuteImpl (System.Int32 index, System.Single aabbMargin, Unity.Mathematics.float3 gravity, System.Single timeStep, Unity.Collections.NativeSlice`1[T] rigidBodies, Unity.Collections.NativeSlice`1[T] motionDatas, Unity.Collections.NativeSlice`1[T] motionVelocities, Unity.Collections.NativeArray`1[T] aabbs, Unity.Collections.NativeArray`1[T] points, Unity.Collections.NativeArray`1[T] filtersOut) (at Library/PackageCache/com.unity.physics@0.3.2-preview/Unity.Physics/Collision/World/Broadphase.cs:810)
Unity.Physics.Broadphase+PrepareDynamicBodyDataJob.Execute (System.Int32 index) (at Library/PackageCache/com.unity.physics@0.3.2-preview/Unity.Physics/Collision/World/Broadphase.cs:790)
Unity.Jobs.IJobParallelForExtensions+ParallelForJobStruct`1[T].Execute (T& jobData, System.IntPtr additionalPtr, System.IntPtr bufferRangePatchData, Unity.Jobs.LowLevel.Unsafe.JobRanges& ranges, System.Int32 jobIndex) (at <94c5f4c38cdc42d2b006f8badef04394>:0)​

 

I looked at this post: https://forum.unity.com/threads/ecs-tear-down-and-restart.539722/

And tried this:

Code (CSharp):

1.    
2. private void OnDestroy()
3.     {
4.         _entityManager.DestroyEntity(_entityManager.UniversalQuery);
5.  
6.         if (_world.IsCreated) {
7.             _world.Dispose();
8.             _world.DestroyAllSystemsAndLogException();
9.         }
10.  
11.         if (_blobStore != null) {
12.             _blobStore.Dispose();
13.         }
14.     }

I now only have one error:

InvalidOperationException: object is not initialized or has already been destroyed
Unity.Entities.ComponentSystemBase.CheckedState () (at Library/PackageCache/com.unity.entities@0.10.0-preview.6/Unity.Entities/ComponentSystemBase.cs:331)
Unity.Entities.ComponentSystem.Update () (at Library/PackageCache/com.unity.entities@0.10.0-preview.6/Unity.Entities/ComponentSystem.cs:86)
Unity.Entities.ScriptBehaviourUpdateOrder+DummyDelegateWrapper.TriggerUpdate () (at Library/PackageCache/com.unity.entities@0.10.0-preview.6/Unity.Entities/ScriptBehaviourUpdateOrder.cs:196)
​

I guess I'll try to find a workaround. Maybe just destroying the entities, and never switching the scene. Just add the menu scene on top.

 

I'm going to assuming that no one has had these issues.

 

Hi!
I have the same issues in my unit tests. I haven't found a way to properly dispose a world and recreate one after.

I assumed it was a bug and didn't have the time to properly debug it. Let me know if you found a workaround!

 

Out of curiosity why do you need to destroy the world?

If you destroy all entities with the universal query, then you shouldn't need to dispose of the world. I know that the systems will still exist, but with no entities to process I doubt they would any kind of noticeable performance impact.

Now if you need to a different world (i.e. a custom bootstrap) for different levels then I could see the need for disposing a world. I'm also curious to know how to do this for this use case.

 

Never tried something like that, but shouldn't you need to use

ScriptBehaviourUpdateOrder.RemoveWorldFromCurrentPlayerLoop(_world)

before destroying all systems?

EDIT: also, I think you need to destroy the systems before disposing the world

Code (CSharp):

1. private void OnDestroy()
2. {
3.     if (_world.IsCreated) {
4.         _entityManager.DestroyEntity(_entityManager.UniversalQuery);
5.         ScriptBehaviourUpdateOrder.RemoveWorldFromCurrentPlayerLoop(_world);
6.         _world.DestroyAllSystemsAndLogException();
7.         _world.Dispose();
8.     }
9.     if (_blobStore != null) {
10.         _blobStore.Dispose();
11.     }
12. }

 

(Disclaimer: Opinion)
This might not be a solution to your problem, but I agree with the notion that you probably shouldn't need to destroy the whole world. Systems shouldn't contain any state to make that necessary. Spawning a set of entities should not lead to different results depending on wether or not similar archetypes existed previously.

 

Or you can clean the state inside OnStopRunning. If it is a System which always update then it may be needed a different approach, but I still think that destroying the World is unnecessary unless you want to create a totally different one later.

 

I was using unity version 2019.3.2f1, and upgraded to 2020.1.0f1 and everything is fine. I think there is a bug with that version.

 

@brunocoimbra I did have try what you had before posting to the forums, and it would still throw exceptions. I think the unity version was the problem.

 

Oh, right, actually ScriptBehaviourUpdateOrder.RemoveWorldFromCurrentPlayerLoop was introduced in Entities 0.13, which is only supported on 2020.1

 

Would this be an good approach for using ScriptBehaviourUpdateOrder.RemoveWorldFromCurrentPlayerLoop()? Because just deleting entities and disposing world still gives some errors in my project.

Code (CSharp):

1. var entitymanager = World.DefaultGameObjectInjectionWorld.EntityManager;
2. entitymanager.DestroyEntity(entitymanager.UniversalQuery);
3. ScriptBehaviourUpdateOrder.RemoveWorldFromCurrentPlayerLoop(World.DefaultGameObjectInjectionWorld);
4. DefaultWorldInitialization.Initialize("Default World", false);
5. SceneManager.LoadScene("World", LoadSceneMode.Single);

After applying this code the systems the hierachy is lost in resetted entities created from the conversion.. I can see all child enities in the hierachy non have an parent. but maybe this could be an bug from DOTS editor