How to get component data from entity of DynamicBuffer?

The buffer like this.

Code (CSharp):

1. public struct MapData:IBufferElementData{
2.     public Entity TileMap;
3. }
4.  

I try to use EntityManager.GetComponentData, but got the error.
ArgumentException: All entities created using EntityCommandBuffer.CreateEntity must be realized via playback(). One of the entities is still deferred (Index: -1)

 

This sounds to me not like a problem with the IBufferElementData, but like you have entities being queued for creation on an EntityCommandBuffer and you're not waiting for it to be replayed before trying to access that entity.

I'm guessing you have something like this:

Code (CSharp):

1. struct MyJob : IJobForEachWithEntity<T>
2. {
3.         public EntityCommandBuffer.Concurrent CommandBuffer;
4.  
5.         public void Execute(Entity entity, int index, ref T component)
6.         {
7.             var newEntity = CommandBuffer.CreateEntity(index);
8.             // then trying to access IBufferElementData on newEntity immediately
9.         }
10. }
11.  

When creating Entities like this, you need to use EntityCommandBufferSystem.AddJobHandleForProducer(JobHandle) and then JobHandle.Complete() before you can access any of the changes made on the EntityCommandBuffer.

 

Show full code

 

As above that shouldn't cause the error you currently see, but you should use
GetBufferFromEntity<BufferElement>() to read dynamic buffers.

See docs: https://docs.unity3d.com/Packages/com.unity.entities@0.0/manual/dynamic_buffers.html

 

trying to make the code clear, here is.

Code (CSharp):

1. public struct Coord : IComponentData{
2.     public int x;
3.     public int y;
4. }
5. public struct TileMap : IComponentData{
6.     public bool isTrap;
7. }
8. public struct MapData:IBufferElementData{
9.     public Entity TileMap;
10. }
11.  
12. public class PathFindingSystem:ComponentSystem{
13.     public EntityQuery mapSpawner;
14.     public int mapWidth=10;
15.     public int mapLength = 10;  
16.     protected override void OnCreate(){
17.         mapSpawner = GetEntityQuery(typeof(MapSpawner));
18.     }
19.  
20.     protected override void OnUpdate(){
21.         var spawner = mapSpawner.GetSingletonEntity();
22.         var mapBuffer = EntityManager.GetBuffer<MapData>(spawner);      
23.         Entities.WithAll<Selecting>().ForEach((Entity entity, ref Coord coord) => {
24.             var tileMapEntity = mapBuffer[coord.x * mapWidth + coord.y].TileMap;
25.             var isTrap = EntityManager.GetComponentData<TileMap>(tileMapEntity).isTrap;
26.             // other code to avoid the trap
27.         });
28.     }
29. }

 

It's not full code, there is nothing which related on you error with EntityCommandBuffer.

 

I guess it's related to the tile map entity created in spawner system, here is.

Code (CSharp):

1. [UpdateInGroup(typeof(SimulationSystemGroup))]
2. class MapSpawnerSystem : JobComponentSystem{
3.     BeginInitializationEntityCommandBufferSystem m_EntityCommandBufferSystem;
4.     protected override void OnCreate()
5.     {
6.         m_EntityCommandBufferSystem = World.GetOrCreateSystem<BeginInitializationEntityCommandBufferSystem>();
7.     }
8.  
9.     [RequireComponentTag ( typeof (ReadyToGen ) ) ]
10.     struct Job:IJobForEachWithEntity<MapSpawner>{
11.         public EntityCommandBuffer ECB;
12.         public BufferFromEntity <MapData> mapBufferLookUp ;
13.      
14.         public void Execute(Entity entity, int index, ref MapSpawner spawner){
15.             var mapBuffer = mapBufferLookUp[entity];
16.             var tiles = new int[spawner.mapWidth, spawner.mapLength];
17.          
18.  
19.             for (int x = 0; x < spawner.mapWidth; x++){
20.                 for (int y = 0; y < spawner.mapLength; y++){
21.                     Entity src = spawner.Prefab;
22.  
23.                     var clone = ECB.Instantiate(src);
24.                     ECB.SetComponent(clone, new Translation{Value = new float3(x,-1f,y)});
25.                  
26.                     var element = new MapData{TileMap = clone};
27.                     // Adding to buffer by order to store the coordinate
28.                     mapBuffer.Add(elelement);
29.                  
30.                 }
31.             }
32.  
33.             ECB.RemoveComponent<ReadyToGen>(entity);
34.         }
35.     }
36.     protected override JobHandle OnUpdate(JobHandle inputDeps){
37.         var job = new Job
38.         {
39.             ECB = m_EntityCommandBufferSystem.CreateCommandBuffer(),
40.             mapBufferLookUp =  GetBufferFromEntity<MapData>(false),
41.          
42.         }.ScheduleSingle(this, inputDeps);
43.         m_EntityCommandBufferSystem.AddJobHandleForProducer(job);
44.  
45.         return job;
46.     }
47. }

 

You can't do this. Because ECB has temporary entities when you create entities, they replaces only after ECB playback. And it's not update any other places where you put this temporary entities.

 

Not necessary, he scheduling it as ScheduleSingle, there is no concurrency afaik.

 

According to the example, if I want to use ecb to create entity and then store it in a native array after creating it, how would I get the right reference?

 

1. Attach a component 'A' to your newly created Entity.
2. Have a job look for entities with 'A'
3. Make said job remove 'A' and then add the entity to your array.

Note that this will have a 1 frame delay if you're doing it in the same system. If you need it the same frame run it ASAP after your ECB has played back.

If you need some data like index to be kept you could just put it in 'A' with ECB.SetComponentData();

 

Thanks for the reply, seems easy enought, Ill try it out

 

access the entity in another system and add to the dynamicbuffer is work