Efficient way to get Player position for targeting

[clear pivot]

Hi, fiddling around in a 2D test project to get a hang of DOTS/ECS. I have a component MoveLinear which has a float2 target and float speed. In my MoveLinearSystem I'm moving the entities towards the target. Problem is, I want the entities to move towards the player, which currently is a normal GameObject.

My first thought is to make the Player class update a static Vector2 variable every frame and then use that in the System, however that upsets the BurstCompiler, since I'm "Loading from a non-readonly static field". I feel like the player position should be stored in ECS and accessed from there, but I'm not exactly sure how to do that efficiently. Any input is appreciated.

[violet valve]

Just have a system that stores player position into component before your MoveLinearSystem

and then get it from component when you need it

[clear pivot]

What component should it store the position in though? Is there a singleton equivalent in Components?

[violet valve]

yes, just call EntityManager.CreateSingleton<T>() in OnCreate and then you can use SystemAPI.SetSingleton(new T()) afterwards

[clear pivot]

Ok yeah that seems good, I'll try it out in a sec.

Can you suggest how I should read the player position though? Do I have to make the Player class a singleton to access the transform?

[violet valve]

well, up to you.
Considering you wanted to use static field - can just store transform in it

[worldly thicket]

Or use SharedStatic to have less code without a system and a component

[clear pivot]

Went over the docs and SharedStatic seems something like a static pointer to a variable, is that correct?

[worldly thicket]

It is a static that can be accesed by bursted code

[violet valve]

it is a static field shared with burst, so it can be used in burst.
But I'd rather avoid it for anything that involves gameplay logic.

[clear pivot]

Yeah in my mind it makes more sense to have a System manage that. However I have run into a problem, don't think the Singleton is created properly. I'm getting an error.

InvalidOperationException: GetSingleton<PlayerPosition>() requires that exactly one entity exists that match this query, but there are none. Are you missing a call to RequireForUpdate<T>()? You could also use TryGetSingleton<T>()

Here's the system class.

[CreateBefore(typeof(MoveLinearSystem))]
public partial class PlayerPositionSystem : SystemBase
{
    public void OnCreate(ref SystemState state) {
        EntityManager.CreateSingleton<PlayerPosition>(new PlayerPosition { positionPlayer = float2.zero}, "PlayerPosition"); 
    }

    public void OnDestroy(ref SystemState state) { 
    }

    protected override void OnUpdate() {
        SystemAPI.SetSingleton(new PlayerPosition { positionPlayer = PlayerMovement.Position });
    }

}```

[violet valve]

show full stack

I feel like it's thrown from different system

[clear pivot]

https://hastebin.com/share/vaxunejapo.csharp

TLDR I'm calling SystemAPI.GetSingleton<PlayerPosition>().positionPlayer in another system's OnUpdate

[violet valve]

until you created singleton it is illegal to call GetSingleton.
So I can only assume that you somehow didn't create that system

[clear pivot]

It's there I believe

[violet valve]

Then maybe you somehow destroyed it?

[clear pivot]

It looks like it's just not calling the OnCreate method for PlayerPositioningSystem. Did I format it wrong?

[violet valve]

oh yeah, you did

SystemBase has virtual methods

ISystem has interface methods