How to use SharedStatic? ECS Burst SystemBase

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So i recently posted a question about accessing and writing to static readonly variables and it has led me to shared static. Does anyone here know how to initialize a shared static variable such as this.

 public static NativeMultiHashMap<int, QuadrantData> quadrantMultiHashMap = new NativeMultiHashMap<int, QuadrantData>(0, Allocator.Persistent);

but in shared static.

Manual: https://docs.unity3d.com/Packages/com.unity.burst@1.2/manual/index.html?_ga=2.116916166.1198962832.1621981940-1822029584.1618698935&_gl=1*17xq55r*_ga*MTgyMjAyOTU4NC4xNjE4Njk4OTM1*_ga_1S78EFL1W5*MTYyMjc1Mjk2OC40OC4xLjE2MjI3NTUyMTguNjA.#shared-static

to be clear the only reason i need this is to write to static readonly variable.

Answer 1

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Answer by andrew-lukasik · Jun 03, 2021 at 11:30 PM

I know what that error message said... but it was misleading in this case. You don't need SharedStatic to fix BC1042 as this is NativeMultiHashMap and you're not synchronizing pointers to different NativeMultiHashMaps across managed-unmanaged memory domains, aren't you?

To the contrary - you have a singleton of type NativeMultiHashMap and just trying to access it's data in different points of your code, which in turn triggers this ambiguous compiler error.

To fix this BC1042 here, you need to stop accessing static fields inside burst-compiled code blocks, that's it.

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andrew-lukasik · Jun 04, 2021 at 10:32 AM 0

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What's more, this doesn't has to be a static field at all. If you remove this static keyword, it will remain accessible from other systems (given dependencies are resolved) as long as it's a public field:

 var quadrantSystem = World.GetExistingSystem<QuadrantSystem>();
 var quadrants = quadrantSystem.quadrantMultiHashMap;

critterawesome andrew-lukasik · Jun 04, 2021 at 02:13 PM 0

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I will try your solution out it seems to be a sensible answer.

critterawesome andrew-lukasik · Jun 04, 2021 at 02:28 PM 0

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we are getting close but another error has popped up insisting that error DC0004: Entities.ForEach Lambda expression captures a non-value type 'quadrantSystem'. This is only allowed with .WithoutBurst() and .Run()

andrew-lukasik critterawesome · Jun 04, 2021 at 05:55 PM 0

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Yes, it is to be expected. Don't reference systems (a class) in a job. Reference structs there only (native hash map is one)

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Answer 2

Answer by critterawesome · Jun 04, 2021 at 08:58 PM

Thanks andrew lukasik! i implemented your suggestion after a long time of errors and debugging and it finally works!

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How to use SharedStatic? ECS Burst SystemBase

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