Question Getting EntityCommandBuffer with SystemState.GetEntityQuery

I am trying to fetch an entity command buffer without using the system API (because I need to simplify some code). So I used SystemState.GetEntityQuery() to make a query in OnCreate() so it will be cached and then later in OnUpdate() I used EntityQuery.TryGetSingleton() to fetch the ECB singleton.

Anyone know why EntityQuery.TryGetSingleton() fails every time? It seems to me like it should work - I can see the singleton exists at runtime in the DOTS inspection tools.

Code (CSharp):

1.  
2.  
3. public struct MyStruct
4. {
5.     EntityQuery m_ecbBeginQuery;
6.  
7.     void MyStruct(ref SystemState state)
8.     {
9.          m_ecbBeginQuery = state.GetEntityQuery(typeof(BeginSimulationEntityCommandBufferSystem.Singleton));
10.     }
11.  
12.     public void CalculateCount() { return m_ecbBeginQuery.CalculateEntityCount();
13.  
14.     public bool TestGetSingleton()
15.     {
16.           return m_ecbBeginQuery.TryGetSingleton<BeginSimulationEntityCommandBufferSystem.Singleton>(out BeginSimulationEntityCommandBufferSystem.Singleton ecbBeginSingleton);
17.     }
18. }
19.  
20. [BurstCompile]
21. public partial struct MySystem : ISystem
22. {
23.     MyStruct m_myStruct;
24.  
25.     void OnCreate(ref SystemState state)
26.     {
27.         // cache the entity query
28.         m_myStruct = new MyStruct(ref state);
29.     }
30.  
31.     [BurstCompile]
32.     void OnUpdate(ref SystemState state)
33.     {
34.         // this always returns zero... why?
35.         int count = m_myStruct.CalculateCount();
36.  
37.         // this always returns false... why?
38.         bool exists = m_myStruct.TestGetSingleton();
39.     }
40. }
41.  

 

It's because the singleton is added to the SystemHandle so you need
WithOptions(EntityQueryOptions.IncludeSystems)

 

Where would you add your suggestion, Tertle? I had the same problem a while ago and I couldn't solve it. Knowing how to fetch and handle a ecb on iSystem would be really useful.

 

On the query builder, either SystemAPI or manual one or on your EntityQueryDesc Options field

SystemAPI.QueryBuilder().WithAll<EndSimulationEntityCommandBufferSystem.Singleton>().WithOptions(EntityQueryOptions.IncludeSystems).Build()