Question Issue with pooling

Hello. I'm getting issues with my projectiles being destroyed instead of despawning back to their pool (using the magical LeanPool.Spawn/Despawn methods). This is what I get in the inspector with a debug in the OnDestroy method of the projectile and I really can't make sense of it:
"
Projectile (Projectile) destroyed instead of returning to the pool
0x00007ff628afed1d (Unity) StackWalker::GetCurrentCallstack
0x00007ff628b058d9 (Unity) StackWalker::ShowCallstack
0x00007ff629a9d0a3 (Unity) GetStacktrace
0x00007ff62a14d05d (Unity) DebugStringToFile
0x00007ff627c607d2 (Unity) DebugLogHandler_CUSTOM_Internal_Log
0x000001765562ca03 (Mono JIT Code) (wrapper managed-to-native) UnityEngine.DebugLogHandler:Internal_Log (UnityEngine.LogType,UnityEngine.LogOption,string,UnityEngine.Object)
0x000001765562c93b (Mono JIT Code) UnityEngine.DebugLogHandler:LogFormat (UnityEngine.LogType,UnityEngine.Object,string,object[])
0x000001765562c6c0 (Mono JIT Code) UnityEngine.Logger:Log (UnityEngine.LogType,object)
0x000001765b3a6fc5 (Mono JIT Code) UnityEngine.Debug:LogError (object)
0x000001765b3a6f6b (Mono JIT Code) [Projectile.cs:16] Projectile:OnDestroy ()
0x0000017655799218 (Mono JIT Code) (wrapper runtime-invoke) object:runtime_invoke_void__this__ (object,intptr,intptr,intptr)
0x00007ffa4811feb4 (mono-2.0-bdwgc) [mini-runtime.c:3445] mono_jit_runtime_invoke
0x00007ffa4805e764 (mono-2.0-bdwgc) [object.c:3066] do_runtime_invoke
0x00007ffa4805e8fc (mono-2.0-bdwgc) [object.c:3113] mono_runtime_invoke
0x00007ff628a22794 (Unity) scripting_method_invoke
0x00007ff628a01f94 (Unity) ScriptingInvocation::Invoke
0x00007ff628a0207e (Unity) ScriptingInvocation::InvokeChecked
0x00007ff628a97d56 (Unity) SerializableManagedRef::CallMethod
0x00007ff6289fc39b (Unity) MonoBehaviour::WillDestroyComponent
0x00007ff6283b3944 (Unity) GameObject::WillDestroyGameObject
0x00007ff6286c2961 (Unity) PreDestroyRecursive
0x00007ff6286c2a48 (Unity) PreDestroyRecursive
0x00007ff6286c08a7 (Unity) DestroyObjectHighLevel_Internal
0x00007ff6286c04e4 (Unity) DestroyObjectHighLevel
0x00007ff6286cae2e (Unity) DestroyWorldObjects
0x00007ff629932c31 (Unity) EditorSceneManager::RestoreSceneBackups
0x00007ff62963b4ed (Unity) PlayerLoopController::ExitPlayMode
0x00007ff62964afe1 (Unity) PlayerLoopController::SetIsPlaying
0x00007ff62964e44b (Unity) Application::TickTimer
0x00007ff629aa323a (Unity) MainMessageLoop
0x00007ff629aa7b0b (Unity) WinMain
0x00007ff62ae86cbe (Unity) __scrt_common_main_seh
0x00007ffa94727614 (KERNEL32) BaseThreadInitThunk
0x00007ffa958c26a1 (ntdll) RtlUserThreadStart"

My projectiles are only referred to in 3 places... The weapon that spawns them with LeanPool.Spawn. The projectile script that calls LeanPool.Despawn OnTriggerEnter. And a timer class that Despawns the object after a certain amount of time (problem still occurs with this timer script disabled). Stranger thing is that the issue doesn't appear right away but maybe 10 or so seconds into firing constantly. Any help would be appreciated!

 

The costs and issues associated with object pooling / pools:

https://forum.unity.com/threads/object-pooling.1329729/#post-8405055

https://forum.unity.com/threads/object-pooling-in-a-tower-defense-game.1076897/#post-6945089

If you insist on pooling anyway, well...

Time to start debugging! Here is how you can begin your exciting new debugging adventures:

You must find a way to get the information you need in order to reason about what the problem is.

Once you understand what the problem is, you may begin to reason about a solution to the problem.

What is often happening in these cases is one of the following:

- the code you think is executing is not actually executing at all
- the code is executing far EARLIER or LATER than you think
- the code is executing far LESS OFTEN than you think
- the code is executing far MORE OFTEN than you think
- the code is executing on another GameObject than you think it is
- you're getting an error or warning and you haven't noticed it in the console window

To help gain more insight into your problem, I recommend liberally sprinkling

Debug.Log()

statements through your code to display information in realtime.

Doing this should help you answer these types of questions:

- is this code even running? which parts are running? how often does it run? what order does it run in?
- what are the names of the GameObjects or Components involved?
- what are the values of the variables involved? Are they initialized? Are the values reasonable?
- are you meeting ALL the requirements to receive callbacks such as triggers / colliders (review the documentation)

Knowing this information will help you reason about the behavior you are seeing.

You can also supply a second argument to Debug.Log() and when you click the message, it will highlight the object in scene, such as

Debug.Log("Problem!",this);

If your problem would benefit from in-scene or in-game visualization, Debug.DrawRay() or Debug.DrawLine() can help you visualize things like rays (used in raycasting) or distances.

You can also call Debug.Break() to pause the Editor when certain interesting pieces of code run, and then study the scene manually, looking for all the parts, where they are, what scripts are on them, etc.

You can also call GameObject.CreatePrimitive() to emplace debug-marker-ish objects in the scene at runtime.

You could also just display various important quantities in UI Text elements to watch them change as you play the game.

Visit Google for how to see console output from builds. If you are running a mobile device you can also view the console output. Google for how on your particular mobile target, such as this answer or iOS: https://forum.unity.com/threads/how-to-capturing-device-logs-on-ios.529920/ or this answer for Android: https://forum.unity.com/threads/how-to-capturing-device-logs-on-android.528680/

If you are working in VR, it might be useful to make your on onscreen log output, or integrate one from the asset store, so you can see what is happening as you operate your software.

Another useful approach is to temporarily strip out everything besides what is necessary to prove your issue. This can simplify and isolate compounding effects of other items in your scene or prefab.

Here's an example of putting in a laser-focused Debug.Log() and how that can save you a TON of time wallowing around speculating what might be going wrong:

https://forum.unity.com/threads/coroutine-missing-hint-and-error.1103197/#post-7100494

"When in doubt, print it out!(tm)" - Kurt Dekker (and many others)

Note: the

print()

function is an alias for Debug.Log() provided by the MonoBehaviour class.

 

I've been debugging this for 3 days now; I know how to debug but this one has got me stumped. My original post is from a debug that I put in the OnDestroy method of my projectile to see if it was indeed getting destroyed. The error doesn't even refer to any of my own scripts which I thought would happen if my own code was causing the destroy. My code is almost as simple as LeanPool.Spawn(projectile) and then inside the OnTriggerEnter of the projectile LeanPool.Despawn(gameObject).

 

Considering this is an issue with an asset store plugin, you should probably ask the tool's developer, and consider whether this may just be a bug in the plugin?

 

https://forum.unity.com/threads/lean-touch-gui-texture-localization-transition-pool.720119/

 

You certainly may have your reasons using a 3rd party pooling, but you can also rely on the builtin pooling provided by Unity itself. I had no issues with that so far.

• https://docs.unity3d.com/ScriptReference/Pool.ObjectPool_1.html

 

Thanks for replies guys. I had scoured for LeanPool issues and bugs but the dev pretty much replied to any of them with "you're definitely destroying the item somewhere". I've considered using the new built in object pooling but had always used LeanPool before with little problem. Probably will look at the built in version now as I don't have too much to change in this project to make it work.

 

Well, have you actually looked at your stacktrace? Especially this part:

Code (CSharp):

1. 0x00007ff6286cae2e (Unity) DestroyWorldObjects
2. 0x00007ff629932c31 (Unity) EditorSceneManager::RestoreSceneBackups
3. 0x00007ff62963b4ed (Unity) PlayerLoopController::ExitPlayMode
4. 0x00007ff62964afe1 (Unity) PlayerLoopController::SetIsPlaying

So the origin is that "is playing" is set to false. So you're exiting playmode and as such the scene and all objects in the scene will be destroyed. Your Projectile script

Code (CSharp):

1. 0x000001765b3a6fc5 (Mono JIT Code) UnityEngine.Debug:LogError (object)
2. 0x000001765b3a6f6b (Mono JIT Code) [Projectile.cs:16] Projectile:OnDestroy ()

Seems to print that error message in line 16.

So I don't quite understand your problem. Do projectiles get destroyed during gameplay? Because what you posted is about the objects getting destroyed when you exit your game which is of course expected.

 

Yes the projectiles are being destroyed at runtime, and the errors come then. Unless the stack trace I've copied is the one generated when I exit playmode, in which case I made a mistake there; but i'm almost positive that my Debug OnDestroy was displaying this during runtime. Not at my PC to confirm but I will later. I'm also getting LeanPool warnings that the Projectile I'm trying to spawn has been destroyed which is why I was using the OnDestroy Debug.Log in the first place

 

But that's the point of having a stacktrace... It shows you who or where the object gets destroyed. So your whole post is kinda misleading. If you don't have actual evidence that you can show here that things get destroyed at runtime this isn't going anywhere

 

Yes, I meant I may have made a mistake and copied over the wrong stack trace when I made this post.

 

To figure out who is destroying your object, put your log message in the OnDisable() method, not OnDestroy(). UnityObject.Destroy() immediately disables the object but the actual destruction is "scheduled" and only happens on the next frame without any hint of where Destroy() was called.

(And no, there's no way for OnDisable to tell the difference between an object being merely disabled versus it being scheduled for destruction: this is one of the many holes in Unity's APIs that's been there since forever and they have shown no intention of willing to fix.)

 

I tried using another 3rd party pooler (that uses UnityEngine.Pool I believe) and after some playing around it seems I only get the errors when a projectile kills an enemy... My enemies are also pooled in a similar fashion. Adding a delay to the despawn of my projectile fixes the problem but I still don't understand why the errors occur anyway.My projectile just knows it hit something, and should despawn. Likewise, my enemy just knows it is dead and should despawn, I don't understand the conflict...

My projectile script:

Code (CSharp):

1. public class Projectile : MonoBehaviour, IDamage
2. {
3.     [SerializeField] private float despawnTime;
4.    
5.     private DamageData data;
6.  
7.     private void OnEnable()
8.     {
9.         StartCoroutine(StartDespawnTimer());
10.     }
11.  
12.     private void OnDisable()
13.     {
14.         StopAllCoroutines();
15.     }
16.  
17.     private void OnTriggerEnter2D(Collider2D collision)
18.     {
19.         if (collision.TryGetComponent(out IDamageable damageable))
20.         {
21.             Damage(damageable);
22.         }
23.         //MasterObjectPooler.Instance.Release(gameObject, "ProjectilePool");
24.         LeanPool.Despawn(gameObject, 0.01f);
25.     }
26.  
27.     public void Initialise(DamageData data)
28.     {
29.         this.data = data;
30.     }
31.  
32.     public void Damage(IDamageable receiver)
33.     {
34.         receiver.TakeDamage(data);
35.     }
36.  
37.     private IEnumerator StartDespawnTimer()
38.     {
39.         yield return new WaitForSeconds(despawnTime);
40.         //MasterObjectPooler.Instance.Release(gameObject, "ProjectilePool");
41.         LeanPool.Despawn(gameObject);
42.     }
43. }
44.  

My Enemies Die() method:

Code (CSharp):

1.     private void Die()
2.     {
3.         EventManager.RaiseEnemyCountChangedEvent(false);
4.         EventManager.RaiseEnemyDeathEvent(experienceValue.Value);
5.         LeanPool.Despawn(gameObject);
6.     }

I'm happy to use the delay for now but it seems a bit hackish - although I will be using delays at some point for enemy death anims etc anyway but stil.

 

Are you sure you don't have any Destroy or DestroyImmediate call in your project? Have you searched through the whole project? Maybe you still have some left over script? Another thing that can "destroy" objects are some of the build in components like a TrailRenderer or the ParticleAnimator of the legacy particle system. Can't think of others at the moment.

Right, haven't thought about that.

 

My project is still very small (like 27 scripts + a few plugins). In the entire project I only use Destroy() once, and that's for a Singleton declaration. I haven't even got as far as adding anything fancy to my projectile or other objects yet; my prototype projectile is just a yellow circle atm.

Also, no difference to the stack trace if the Debug is in OnDisable instead of OnDestroy (although the original post was the incorrect one from exiting play mode). Here's the callstacks for both projectiles that despawn to pool correctly, and incorrectly respectively:

Code (CSharp):

1. Projectile disabled
2. 0x00007ff60c26ed1d (Unity) StackWalker::GetCurrentCallstack
3. 0x00007ff60c2758d9 (Unity) StackWalker::ShowCallstack
4. 0x00007ff60d20d0a3 (Unity) GetStacktrace
5. 0x00007ff60d8bd05d (Unity) DebugStringToFile
6. 0x00007ff60b3d07d2 (Unity) DebugLogHandler_CUSTOM_Internal_Log
7. 0x000001fa43f44603 (Mono JIT Code) (wrapper managed-to-native) UnityEngine.DebugLogHandler:Internal_Log (UnityEngine.LogType,UnityEngine.LogOption,string,UnityEngine.Object)
8. 0x000001fa43f4451b (Mono JIT Code) UnityEngine.DebugLogHandler:LogFormat (UnityEngine.LogType,UnityEngine.Object,string,object[])
9. 0x000001fa43f44260 (Mono JIT Code) UnityEngine.Logger:Log (UnityEngine.LogType,object)
10. 0x000001fa43f44128 (Mono JIT Code) UnityEngine.Debug:Log (object)
11. 0x000001fa44010a93 (Mono JIT Code) [Projectile.cs:20] Projectile:OnDisable ()
12. 0x000001fa443904e8 (Mono JIT Code) (wrapper runtime-invoke) object:runtime_invoke_void__this__ (object,intptr,intptr,intptr)
13. 0x00007ffa3b50feb4 (mono-2.0-bdwgc) [mini-runtime.c:3445] mono_jit_runtime_invoke
14. 0x00007ffa3b44e764 (mono-2.0-bdwgc) [object.c:3066] do_runtime_invoke
15. 0x00007ffa3b44e8fc (mono-2.0-bdwgc) [object.c:3113] mono_runtime_invoke
16. 0x00007ff60c192794 (Unity) scripting_method_invoke
17. 0x00007ff60c171f94 (Unity) ScriptingInvocation::Invoke
18. 0x00007ff60c17207e (Unity) ScriptingInvocation::InvokeChecked
19. 0x00007ff60c207d56 (Unity) SerializableManagedRef::CallMethod
20. 0x00007ff60c164912 (Unity) MonoBehaviour::RemoveFromManager
21. 0x00007ff60bb1a29d (Unity) GameObject::ActivateAwakeRecursivelyInternal
22. 0x00007ff60bb19ea9 (Unity) GameObject::ActivateAwakeRecursively
23. 0x00007ff60bb21d17 (Unity) GameObject::SetSelfActive
24. 0x00007ff60b3c9c0b (Unity) GameObject_CUSTOM_SetActive
25. 0x000001fa43ef080c (Mono JIT Code) (wrapper managed-to-native) UnityEngine.GameObject:SetActive (UnityEngine.GameObject,bool)
26. 0x000001fa4898806b (Mono JIT Code) [LeanGameObjectPool.cs:715] Lean.Pool.LeanGameObjectPool:DespawnNow (UnityEngine.GameObject,bool)
27. 0x000001fa48987e93 (Mono JIT Code) [LeanGameObjectPool.cs:691] Lean.Pool.LeanGameObjectPool:TryDespawn (UnityEngine.GameObject)
28. 0x000001fa48987563 (Mono JIT Code) [LeanGameObjectPool.cs:411] Lean.Pool.LeanGameObjectPool:Despawn (UnityEngine.GameObject,single)
29. 0x000001fa48987373 (Mono JIT Code) [LeanPool.cs:153] Lean.Pool.LeanPool:Despawn (UnityEngine.GameObject,single)
30. 0x000001fa48973d3b (Mono JIT Code) [Projectile.cs:31] Projectile:OnTriggerEnter2D (UnityEngine.Collider2D)
31. 0x000001fa4695dcb3 (Mono JIT Code) (wrapper runtime-invoke) <Module>:runtime_invoke_void__this___object (object,intptr,intptr,intptr)
32. 0x00007ffa3b50feb4 (mono-2.0-bdwgc) [mini-runtime.c:3445] mono_jit_runtime_invoke
33. 0x00007ffa3b44e764 (mono-2.0-bdwgc) [object.c:3066] do_runtime_invoke
34. 0x00007ffa3b44e8fc (mono-2.0-bdwgc) [object.c:3113] mono_runtime_invoke
35. 0x00007ff60c192794 (Unity) scripting_method_invoke
36. 0x00007ff60c171f94 (Unity) ScriptingInvocation::Invoke
37. 0x00007ff60c15faec (Unity) MonoBehaviour::HandleNotifications
38. 0x00007ff60bb213ab (Unity) GameObject::SendMessageAny
39. 0x00007ff60c883866 (Unity) PhysicsContacts2D::SendCallbackReports
40. 0x00007ff60c881d71 (Unity) PhysicsContacts2D::ProcessContacts
41. 0x00007ff60c851c58 (Unity) PhysicsManager2D::Simulate
42. 0x00007ff60c84e18f (Unity) PhysicsManager2D::FixedUpdate
43. 0x00007ff60c84e2d6 (Unity) `PhysicsManager2D::Initialize'::`2'::FixedUpdatePhysics2DFixedUpdateRegistrator::Forward
44. 0x00007ff60be468ba (Unity) ExecutePlayerLoop
45. 0x00007ff60be46a46 (Unity) ExecutePlayerLoop
46. 0x00007ff60be4cb29 (Unity) PlayerLoop
47. 0x00007ff60cdbffb9 (Unity) PlayerLoopController::UpdateScene
48. 0x00007ff60cdbe15b (Unity) Application::TickTimer
49. 0x00007ff60d21323a (Unity) MainMessageLoop
50. 0x00007ff60d217b0b (Unity) WinMain
51. 0x00007ff60e5f6cbe (Unity) __scrt_common_main_seh
52. 0x00007ffa94727614 (KERNEL32) BaseThreadInitThunk
53. 0x00007ffa958c26a1 (ntdll) RtlUserThreadStart

Code (CSharp):

1. Projectile disabled
2. 0x00007ff60c26ed1d (Unity) StackWalker::GetCurrentCallstack
3. 0x00007ff60c2758d9 (Unity) StackWalker::ShowCallstack
4. 0x00007ff60d20d0a3 (Unity) GetStacktrace
5. 0x00007ff60d8bd05d (Unity) DebugStringToFile
6. 0x00007ff60b3d07d2 (Unity) DebugLogHandler_CUSTOM_Internal_Log
7. 0x000001fa43f44603 (Mono JIT Code) (wrapper managed-to-native) UnityEngine.DebugLogHandler:Internal_Log (UnityEngine.LogType,UnityEngine.LogOption,string,UnityEngine.Object)
8. 0x000001fa43f4451b (Mono JIT Code) UnityEngine.DebugLogHandler:LogFormat (UnityEngine.LogType,UnityEngine.Object,string,object[])
9. 0x000001fa43f44260 (Mono JIT Code) UnityEngine.Logger:Log (UnityEngine.LogType,object)
10. 0x000001fa43f44128 (Mono JIT Code) UnityEngine.Debug:Log (object)
11. 0x000001fa44010a93 (Mono JIT Code) [Projectile.cs:20] Projectile:OnDisable ()
12. 0x000001fa443904e8 (Mono JIT Code) (wrapper runtime-invoke) object:runtime_invoke_void__this__ (object,intptr,intptr,intptr)
13. 0x00007ffa3b50feb4 (mono-2.0-bdwgc) [mini-runtime.c:3445] mono_jit_runtime_invoke
14. 0x00007ffa3b44e764 (mono-2.0-bdwgc) [object.c:3066] do_runtime_invoke
15. 0x00007ffa3b44e8fc (mono-2.0-bdwgc) [object.c:3113] mono_runtime_invoke
16. 0x00007ff60c192794 (Unity) scripting_method_invoke
17. 0x00007ff60c171f94 (Unity) ScriptingInvocation::Invoke
18. 0x00007ff60c17207e (Unity) ScriptingInvocation::InvokeChecked
19. 0x00007ff60c207d56 (Unity) SerializableManagedRef::CallMethod
20. 0x00007ff60c164912 (Unity) MonoBehaviour::RemoveFromManager
21. 0x00007ff60bb1a29d (Unity) GameObject::ActivateAwakeRecursivelyInternal
22. 0x00007ff60bb19ea9 (Unity) GameObject::ActivateAwakeRecursively
23. 0x00007ff60bb21d17 (Unity) GameObject::SetSelfActive
24. 0x00007ff60b3c9c0b (Unity) GameObject_CUSTOM_SetActive
25. 0x000001fa43ef080c (Mono JIT Code) (wrapper managed-to-native) UnityEngine.GameObject:SetActive (UnityEngine.GameObject,bool)
26. 0x000001fa4898806b (Mono JIT Code) [LeanGameObjectPool.cs:715] Lean.Pool.LeanGameObjectPool:DespawnNow (UnityEngine.GameObject,bool)
27. 0x000001fa48987e93 (Mono JIT Code) [LeanGameObjectPool.cs:691] Lean.Pool.LeanGameObjectPool:TryDespawn (UnityEngine.GameObject)
28. 0x000001fa48987563 (Mono JIT Code) [LeanGameObjectPool.cs:411] Lean.Pool.LeanGameObjectPool:Despawn (UnityEngine.GameObject,single)
29. 0x000001fa48987373 (Mono JIT Code) [LeanPool.cs:153] Lean.Pool.LeanPool:Despawn (UnityEngine.GameObject,single)
30. 0x000001fa48973d3b (Mono JIT Code) [Projectile.cs:31] Projectile:OnTriggerEnter2D (UnityEngine.Collider2D)
31. 0x000001fa4695dcb3 (Mono JIT Code) (wrapper runtime-invoke) <Module>:runtime_invoke_void__this___object (object,intptr,intptr,intptr)
32. 0x00007ffa3b50feb4 (mono-2.0-bdwgc) [mini-runtime.c:3445] mono_jit_runtime_invoke
33. 0x00007ffa3b44e764 (mono-2.0-bdwgc) [object.c:3066] do_runtime_invoke
34. 0x00007ffa3b44e8fc (mono-2.0-bdwgc) [object.c:3113] mono_runtime_invoke
35. 0x00007ff60c192794 (Unity) scripting_method_invoke
36. 0x00007ff60c171f94 (Unity) ScriptingInvocation::Invoke
37. 0x00007ff60c15faec (Unity) MonoBehaviour::HandleNotifications
38. 0x00007ff60bb213ab (Unity) GameObject::SendMessageAny
39. 0x00007ff60c8838ad (Unity) PhysicsContacts2D::SendCallbackReports
40. 0x00007ff60c881d71 (Unity) PhysicsContacts2D::ProcessContacts
41. 0x00007ff60c851c58 (Unity) PhysicsManager2D::Simulate
42. 0x00007ff60c84e18f (Unity) PhysicsManager2D::FixedUpdate
43. 0x00007ff60c84e2d6 (Unity) `PhysicsManager2D::Initialize'::`2'::FixedUpdatePhysics2DFixedUpdateRegistrator::Forward
44. 0x00007ff60be468ba (Unity) ExecutePlayerLoop
45. 0x00007ff60be46a46 (Unity) ExecutePlayerLoop
46. 0x00007ff60be4cb29 (Unity) PlayerLoop
47. 0x00007ff60cdbffb9 (Unity) PlayerLoopController::UpdateScene
48. 0x00007ff60cdbe15b (Unity) Application::TickTimer
49. 0x00007ff60d21323a (Unity) MainMessageLoop
50. 0x00007ff60d217b0b (Unity) WinMain
51. 0x00007ff60e5f6cbe (Unity) __scrt_common_main_seh
52. 0x00007ffa94727614 (KERNEL32) BaseThreadInitThunk
53. 0x00007ffa958c26a1 (ntdll) RtlUserThreadStart

From what I can see everything is exactly the same EXCEPT:
0x00007ff60c883866 (Unity) PhysicsContacts2D::SendCallbackReports
becomes:
0x00007ff60c8838ad (Unity) PhysicsContacts2D::SendCallbackReports

Unfortunately this is beyond my level of understanding, and I'm not even sure if it means anything. Although I'm suspecting it has something to do with the physics of my projectile and enemy conflicting somehow.

 

How do you determine that the despawn was incorrectly? The object wasn't destroyed in both cases. The object was just deactivated because SetActive was called in responds to being returned to the pool. Do you actually get any OnDestroy calls beside those from unloading the scene? If you have trouble to "match" the OnDestroy and OnDisable calls, you can always give your Projectile instances a unique ID. Just add this to the Projectile class:

Code (CSharp):

1. private static int m_IDCounter = 0;
2. private int m_ID = m_IDCounter++;
3.  
4. void OnDestroy()
5. {
6.     Debug.Log("Destroy Projectile #"+m_ID+" at frame " + Time.frameCount);
7. }
8. void OnDisable()
9. {
10.     Debug.Log("Disable Projectile #"+m_ID+" at frame " + Time.frameCount);
11. }
12. void OnEnable()
13. {
14.     Debug.Log("Enable Projectile #"+m_ID+" at frame " + Time.frameCount);
15. }
16.  

This way you can actually identify every Projectile instance by it's ID. No two instances would have the same id (unless you create more than 4 billion). You also see the actual frame the callback happens. So if an object is actually destroyed, the corresponding disable log would at most be 1 frame apart, but I think it should still be the same frame, just later at the end of the frame.

 

Thanks for that @Bunny83. I didn't think to assign them seperate ID's. Anyhow, it seems (almost randomly) that sometimes my projectile will get destroyed and disabled on the same frame:



Stacktraces for each:

Code (CSharp):

1. Disable Projectile #8 at frame 7548
2. 0x00007ff7963aed1d (Unity) StackWalker::GetCurrentCallstack
3. 0x00007ff7963b58d9 (Unity) StackWalker::ShowCallstack
4. 0x00007ff79734d0a3 (Unity) GetStacktrace
5. 0x00007ff7979fd05d (Unity) DebugStringToFile
6. 0x00007ff7955107d2 (Unity) DebugLogHandler_CUSTOM_Internal_Log
7. 0x00000277c540b003 (Mono JIT Code) (wrapper managed-to-native) UnityEngine.DebugLogHandler:Internal_Log (UnityEngine.LogType,UnityEngine.LogOption,string,UnityEngine.Object)
8. 0x00000277c540af1b (Mono JIT Code) UnityEngine.DebugLogHandler:LogFormat (UnityEngine.LogType,UnityEngine.Object,string,object[])
9. 0x00000277c540ac60 (Mono JIT Code) UnityEngine.Logger:Log (UnityEngine.LogType,object)
10. 0x00000277c540ab28 (Mono JIT Code) UnityEngine.Debug:Log (object)
11. 0x00000277cb3fbc0b (Mono JIT Code) [Projectile.cs:28] Projectile:OnDisable ()
12. 0x00000277cb33c0e8 (Mono JIT Code) (wrapper runtime-invoke) object:runtime_invoke_void__this__ (object,intptr,intptr,intptr)
13. 0x00007ffa4631feb4 (mono-2.0-bdwgc) [mini-runtime.c:3445] mono_jit_runtime_invoke
14. 0x00007ffa4625e764 (mono-2.0-bdwgc) [object.c:3066] do_runtime_invoke
15. 0x00007ffa4625e8fc (mono-2.0-bdwgc) [object.c:3113] mono_runtime_invoke
16. 0x00007ff7962d2794 (Unity) scripting_method_invoke
17. 0x00007ff7962b1f94 (Unity) ScriptingInvocation::Invoke
18. 0x00007ff7962b207e (Unity) ScriptingInvocation::InvokeChecked
19. 0x00007ff796347d56 (Unity) SerializableManagedRef::CallMethod
20. 0x00007ff7962a4912 (Unity) MonoBehaviour::RemoveFromManager
21. 0x00007ff795c5a29d (Unity) GameObject::ActivateAwakeRecursivelyInternal
22. 0x00007ff795c59ea9 (Unity) GameObject::ActivateAwakeRecursively
23. 0x00007ff795c61d17 (Unity) GameObject::SetSelfActive
24. 0x00007ff795509c0b (Unity) GameObject_CUSTOM_SetActive
25. 0x00000277c53b3bdc (Mono JIT Code) (wrapper managed-to-native) UnityEngine.GameObject:SetActive (UnityEngine.GameObject,bool)
26. 0x00000277cb3fb80b (Mono JIT Code) [LeanGameObjectPool.cs:715] Lean.Pool.LeanGameObjectPool:DespawnNow (UnityEngine.GameObject,bool)
27. 0x00000277cb3fb633 (Mono JIT Code) [LeanGameObjectPool.cs:691] Lean.Pool.LeanGameObjectPool:TryDespawn (UnityEngine.GameObject)
28. 0x00000277cb3fb4a3 (Mono JIT Code) [LeanGameObjectPool.cs:411] Lean.Pool.LeanGameObjectPool:Despawn (UnityEngine.GameObject,single)
29. 0x00000277cb3fb2b3 (Mono JIT Code) [LeanPool.cs:153] Lean.Pool.LeanPool:Despawn (UnityEngine.GameObject,single)
30. 0x00000277cb3fb143 (Mono JIT Code) [Projectile.cs:34] Projectile:OnTriggerEnter2D (UnityEngine.Collider2D)
31. 0x00000277cb3e2b43 (Mono JIT Code) (wrapper runtime-invoke) <Module>:runtime_invoke_void__this___object (object,intptr,intptr,intptr)
32. 0x00007ffa4631feb4 (mono-2.0-bdwgc) [mini-runtime.c:3445] mono_jit_runtime_invoke
33. 0x00007ffa4625e764 (mono-2.0-bdwgc) [object.c:3066] do_runtime_invoke
34. 0x00007ffa4625e8fc (mono-2.0-bdwgc) [object.c:3113] mono_runtime_invoke
35. 0x00007ff7962d2794 (Unity) scripting_method_invoke
36. 0x00007ff7962b1f94 (Unity) ScriptingInvocation::Invoke
37. 0x00007ff79629faec (Unity) MonoBehaviour::HandleNotifications
38. 0x00007ff795c613ab (Unity) GameObject::SendMessageAny
39. 0x00007ff7969c3866 (Unity) PhysicsContacts2D::SendCallbackReports
40. 0x00007ff7969c1d71 (Unity) PhysicsContacts2D::ProcessContacts
41. 0x00007ff796991c58 (Unity) PhysicsManager2D::Simulate
42. 0x00007ff79698e18f (Unity) PhysicsManager2D::FixedUpdate
43. 0x00007ff79698e2d6 (Unity) `PhysicsManager2D::Initialize'::`2'::FixedUpdatePhysics2DFixedUpdateRegistrator::Forward
44. 0x00007ff795f868ba (Unity) ExecutePlayerLoop
45. 0x00007ff795f86a46 (Unity) ExecutePlayerLoop
46. 0x00007ff795f8cb29 (Unity) PlayerLoop
47. 0x00007ff796efffb9 (Unity) PlayerLoopController::UpdateScene
48. 0x00007ff796efe15b (Unity) Application::TickTimer
49. 0x00007ff79735323a (Unity) MainMessageLoop
50. 0x00007ff797357b0b (Unity) WinMain
51. 0x00007ff798736cbe (Unity) __scrt_common_main_seh
52. 0x00007ffa94727614 (KERNEL32) BaseThreadInitThunk
53. 0x00007ffa958c26a1 (ntdll) RtlUserThreadStart

Code (CSharp):

1. Destroy Projectile #8 at frame 7548
2. 0x00007ff7963aed1d (Unity) StackWalker::GetCurrentCallstack
3. 0x00007ff7963b58d9 (Unity) StackWalker::ShowCallstack
4. 0x00007ff79734d0a3 (Unity) GetStacktrace
5. 0x00007ff7979fd05d (Unity) DebugStringToFile
6. 0x00007ff7955107d2 (Unity) DebugLogHandler_CUSTOM_Internal_Log
7. 0x00000277c540b003 (Mono JIT Code) (wrapper managed-to-native) UnityEngine.DebugLogHandler:Internal_Log (UnityEngine.LogType,UnityEngine.LogOption,string,UnityEngine.Object)
8. 0x00000277c540af1b (Mono JIT Code) UnityEngine.DebugLogHandler:LogFormat (UnityEngine.LogType,UnityEngine.Object,string,object[])
9. 0x00000277c540ac60 (Mono JIT Code) UnityEngine.Logger:Log (UnityEngine.LogType,object)
10. 0x00000277c540ab28 (Mono JIT Code) UnityEngine.Debug:Log (object)
11. 0x000002787fb6521b (Mono JIT Code) [Projectile.cs:17] Projectile:OnDestroy ()
12. 0x00000277cb33c0e8 (Mono JIT Code) (wrapper runtime-invoke) object:runtime_invoke_void__this__ (object,intptr,intptr,intptr)
13. 0x00007ffa4631feb4 (mono-2.0-bdwgc) [mini-runtime.c:3445] mono_jit_runtime_invoke
14. 0x00007ffa4625e764 (mono-2.0-bdwgc) [object.c:3066] do_runtime_invoke
15. 0x00007ffa4625e8fc (mono-2.0-bdwgc) [object.c:3113] mono_runtime_invoke
16. 0x00007ff7962d2794 (Unity) scripting_method_invoke
17. 0x00007ff7962b1f94 (Unity) ScriptingInvocation::Invoke
18. 0x00007ff7962b207e (Unity) ScriptingInvocation::InvokeChecked
19. 0x00007ff796347d56 (Unity) SerializableManagedRef::CallMethod
20. 0x00007ff7962ac39b (Unity) MonoBehaviour::WillDestroyComponent
21. 0x00007ff795c63944 (Unity) GameObject::WillDestroyGameObject
22. 0x00007ff795f72961 (Unity) PreDestroyRecursive
23. 0x00007ff795f708a7 (Unity) DestroyObjectHighLevel_Internal
24. 0x00007ff795f704e4 (Unity) DestroyObjectHighLevel
25. 0x00007ff795d8b47b (Unity) DelayedDestroyCallback
26. 0x00007ff795d8cf64 (Unity) DelayedCallManager::Update
27. 0x00007ff795f9f8f2 (Unity) `InitPlayerLoopCallbacks'::`2'::FixedUpdateScriptRunDelayedFixedFrameRateRegistrator::Forward
28. 0x00007ff795f868ba (Unity) ExecutePlayerLoop
29. 0x00007ff795f86a46 (Unity) ExecutePlayerLoop
30. 0x00007ff795f8cb29 (Unity) PlayerLoop
31. 0x00007ff796efffb9 (Unity) PlayerLoopController::UpdateScene
32. 0x00007ff796efe15b (Unity) Application::TickTimer
33. 0x00007ff79735323a (Unity) MainMessageLoop
34. 0x00007ff797357b0b (Unity) WinMain
35. 0x00007ff798736cbe (Unity) __scrt_common_main_seh
36. 0x00007ffa94727614 (KERNEL32) BaseThreadInitThunk
37. 0x00007ffa958c26a1 (ntdll) RtlUserThreadStart

Going by this you would think it was a bug with LeanPool, but I've tried other pooling methods with similar results. I can't see anything in the OnDestroy stacktrace that relates to my own code, and the OnDisable stacktrace looks to function correctly by Despawing OnTriggerEnter.

Also, worth noting is that if I do a gameobject.activeself check before calling LeanPool.Despawn, the errors go away. I'm so confused as to what else could possibly be disabling the projectiles!