Question Per-System Entities, How do you get them?

Hey there! I have a question in regards to these per-system entities that was introduced with experimental 1.0, it does make sense to work with these system entities but we're not sure about the means of getting these entities.

We saw there is the "UniversalQueryWithSystems" method but this looks to be heavy. I wanted to see if someone found some cleaner way to asking for these per-system entities. I saw that the entity is stored in the SystemHandle instance. And I'm also not sure of what's happening here with SystemInstance

Code (CSharp):

1. var systemComponent = ComponentType.ReadWrite<SystemInstance>();
2. Entity systemEntity = self.EntityManager.CreateEntity(self.EntityManager.CreateArchetype(&systemComponent, 1));

Thanks in advance!

 

I also was trying to figure out how to use "system entities".

There is a mention in entities 1.0 changelog:

1. I can use

   EntityManager.UniversalQueryWithSystems

   but it returns a lot of unnecessary entities, not only system entities.
   
   
2. I can create my own custom query

   new EntityQueryBuilder(Allocator.Temp).WithOptions(EntityQueryOptions.IncludeSystems)

   but it returns the same.
   
   
3. I can get the system entity using C# reflection:
   
   Code (CSharp):

   1. SystemHandle handle = EntityManager.World.GetExistingSystem<MySystem>();
   2. Entity systemEntity = (Entity) typeof(SystemHandle).GetField("m_Entity", BindingFlags.Instance | BindingFlags.NonPublic)?.GetValue(handle)!;
   3. Debug.Log( $"systemEntity: {systemEntity.Index}" );
   but I don't feel this is appropriate way

So, how should we use it?

 

https://docs.unity3d.com/Packages/c...ComponentData__1_Unity_Entities_SystemHandle_

And the other methods have overloads as well for taking in a SystemHandle (which you can get with either state.SystemHandle for ISystem or this.SystemHandle for SystemBase).

 

You aren't really meant to get them I guess. Instead you should kind of pretend the entity doesn't actually exist and instead you are just adding or removing data (components) to the system itself.

As Luxxuor said you can use the system handle overloads to achieve this.

 

but addBuffer require an entity, systemHandle is not useful in this case.

 

Also seems like some of the command-buffer methods dont have sytem-handle overloads, such as RemoveComponent.

 

I have stumbled upon the same question. If adding componentdata to system is preferred way of storing per system data, then we should have AddBuffer accepting the systemhandle?

GetBuffer accepts systemhandle, but AddBuffer does not. Makes no sense?