Entities.With() : Proper way to access Components?

The docs and package test code don't actually have an example of accessing and modifying component data in a ComponentSystem using Entities.With(). They just have

//do stuff

I'm using an exiting EntityQuery.

Do I just use EntityManager.Get/SetComponentData() or is there a better/more efficient way?

I realize that ComponentSystem is not efficient, but I have a small number of entities to iterate over and only once in a while. The problem is a bit a hard to parallelize 'til I prototype it, so this seemed a simple way to get it working.

Current simplified version for example only:

Code (CSharp):

1.         protected override void OnUpdate()
2.         {
3.             Entities.With(allRootsGroup).ForEach((Entity entity) =>
4.             {
5.                 // Debug.Log("Root "+entity);
6.                 if (EntityManager.HasComponent<PlayerInput>(entity))
7.                 {
8.                     var order = EntityManager.GetComponentData<PlayerInput>(entity);
9.                     //more complex stuff happens here
10.                     EntityManager.SetComponentData(entity, new Goal
11.                     {
12.                         Value = order.Goal
13.                     });
14.                 }
15.                 else {
16.                   // do other stuff
17.                 }
18.             });
19.         }

 

Ah, I can use generics, though I don't know if this is much faster.Also I cant; use Buffers as args i the lambda.

Code (CSharp):

1.         protected override void OnUpdate()
2.         {
3.             Entities.With(allRootsGroup).ForEach<Goal>((Entity entity, ref Goal goal) =>
4.             {
5.                  var children = EntityManager.GetBuffer<MyChild>(entity);
6.  
7.                 // Debug.Log("Root "+entity);
8.                 if (EntityManager.HasComponent<PlayerInput>(entity))
9.                 {
10.                     var order = EntityManager.GetComponentData<PlayerInput>(entity);
11.                     goal.Value = order.Goal;
12.                 } else {
13.                   // do other stuff
14.                 }
15.             });
16.         }

 

In your first example it would be as easy as this:

Code (CSharp):

1.     Entities.With(allRootsGroup).ForEach((ref PlayerInput input, ref Goal goal) =>
2.     {
3.       goal.Value = input.Goal;
4.     });

 

This code would only work if you are sure PlayerInput is on all entities of the group.
The reason he use With() (and that he check if there is a PlayerInput component) instead of WithAll() is that some components can be present or not, if he access to a component that is not present on an entity, he can have a nullref exception.

 

You can use buffers in ForEach:

Code (CSharp):

1.  
2. Entities.WithAll(allRootsGroup).ForEach((Entity entity, DynamicBuffer<MyChild> children, ref Goal goal) =>
3. {
4.     // your stuff
5. });
6.  

 

I've missed that possibility.
In that case you can use:

Code (CSharp):

1.     Entities.With(allRootsGroup).ForEach((ref PlayerInput input, ref Goal goal) => {
2.       if(UnsafeUtility.AddressOf(ref input) != null && UnsafeUtility.AddressOf(ref goal) != null)
3.         goal.Value = input.Goal;
4.     });