How to interact with entities from Monobehaviour?

i have lot of cases where i need to access entity data from monobehaviour, EG get its position and spawn player there



I see theres entitymanager.getallentities, but that will always get me an array of 40000 its very bad function IMO

now the question is how to easily interact with some of entities? from mb

 

You can use EntityManager for these cases:
- Store "reference" to entity that is converted / created to the Monobehaviour. Access data via that entity by using EntityManager;
- Use a query to fetch specific entities. (E.g. tag + position + ...) - then fetch data via received entities;
- Use singleton (GetSingletonEntity / GetSingleton) utility to fetch entity / component data.

Queries can be created from EntityManager (just in case).

 

oh ok do you know why GetComponentData<Child> specifically doesnt work and any way to make it work?

i already made list of top level entities that i have on static class. but now i cant get their child

 

Post the code, and errors it produces. Its hard to debug without it.

 

Because

Child

is

IBufferElementData

and you should access it differently:

GetBuffer<Child>

 

How do you test if it exists?

If you try and GetBuffer from an entity without an IBufferElementData, it errors out:

ArgumentException: A component with type:myElement [Buffer] has not been added to the entity.

 

Code (CSharp):

1. EntityManager.HasComponent<MyBuffer>(entity);

works for buffers too, in fact all types afaik.

 

Yes, thank you. Items are dropping in my game now one at a time.

 

How can I use GetSingletonEntity from Monobehaviour?

 

1. Get an EntityManager (e.g. from the World.DefaultGameObjectInjectionWorld);
2. Construct EntityManager.CreateEntityQuery (can be cached somewhere for whole MonoBehaviour side if no more than one world is used);
3. Use GetSingleton / GetSingletonEntity from EntityQuery;

 

Should

be cached, otherwise should be disposed before next

EntityManager.CreateEntityQuery

, as every call (even with the same components) will create new instance and you'll see memory leak.

 

I asked for something like this and this is what we came up with:

https://forum.unity.com/threads/best-practice-for-getting-references-to-gameobjects.1034962/