AddEntity with Templates

[Selmar]

Description

World.AddEntity exists for creating new entities via tags. This works great, but for authoring this requires to create a script for each template. As a simple intermediate solution for authoring, I'd like to be able to add entities with a Template instance as well.

Use Case

This would make it possible to create authoring scripts more easily, via class Authoring<T> : Authoring where T : ITemplate { ... }.

Proposed Solution

No response

Alternatives Considered

An alternative way to help automate authoring would be to use code-gen to generate authoring scripts for templates, and editor scripts for the components. That is probably my long-term solution.

[svermeulen]

Can you elaborate on how these authoring scripts would work? Are you looking for a solution similar to Unity ECS where you can configure entities in a MonoBehaviour?

At one point I considered something like this. For example, we could source generate a static Create method on the ITemplate derived class that took all required components, and maybe optional nullable parameters for any optional components (where optional is indicated by the lack of a default value in the ITemplate class definition). That would be nice because you'd get compile errors if you make a component required, or add/remove components. Currently the ITemplate derived class is never actually instantiated and is more just used as a DSL

In my view, in most cases, I think it's best to keep systems decoupled from templates. Systems only declare the tags and the components they are interested in. It keeps things maximally loosely coupled. If a system did a query based on a template reference then they become tightly coupled to the run configuration, so can't easily run that system in tests, or in other run configurations.

This is less true for AddEntity though since it's common to need to fully specify the initial state so probably there is something useful we could do here

[Selmar]

Can you elaborate on how these authoring scripts would work? Are you looking for a solution similar to Unity ECS where you can configure entities in a MonoBehaviour?

My main goal for now is just to get something I can prototype with, not necessarily a perfect solution.

Right now, indeed, I use MonoBehaviours. I do it this way is simply because it's the most practical, especially if I intend to have scene objects linked to entities later on (t.b.d.). Currently I have a base "authoring" class that I use to initialize the runtime with. I get all of them with a find objects of type, and iterate over them in the scene initializer.

	public abstract class Authoring : MonoBehaviour
	{
		public abstract void Initialize(SceneInitializer initializer);
	}

I do agree with your comments on templates. At runtime, anyway, if I want to identify a specific template, all I need to do is make sure it has a unique tag. I also don't think AddEntity<ITemplate> is the end goal; I would prefer to create a proper codegen solution. The issue is that that will take a non-negligible* amount of time, so I consider this a reasonable workaround.

[svermeulen]

We will have to revisit this issue when/if we add support for scene based monobehaviour authoring similar to what UECS does with subscenes. The Trecs Hierarchy window populates the unity inspector with component values so could do something similar for this kind of workflow potentially