Passing a List from Baker class to Entity-based Component

Unity Engine
, ,
1

I have the following code snippet:

public class MyDataAuthoring : MonoBehaviour
{
    public List<int> ItemIds;
    public int value;

    private class Baker : Baker<MyDataAuthoring >
    {
        public override void Bake(MyDataAuthoring authoring)
        {
            Entity entity = GetEntity(TransformUsageFlags.Renderable);
            AddComponent(entity, new MyData{
                //Pass ItemIds
                value = authoring.value
            });
        }
    }
}
public struct MyData : IComponentData
{
    //Pass ItemIds List to some Blittable type
    public int value;
}

My aim is to pass ItemIds from MyDataAuthoring to MyData. How can I achieve this?

2

Are you familiar with DynamicBuffer and the IBufferElementData types?

3

I did have a brief look at it and this is what I came up with:

public class MyDataAuthoring : MonoBehaviour
{
    public List<int> ItemIds;
    public int value;

    private class Baker : Baker<MyDataAuthoring>
    {
        public override void Bake(MyDataAuthoring authoring)
        {
            DynamicBuffer<int> ids = new DynamicBuffer<int>();

            for(int i = 0; i < authoring.ItemIds.Count; ++i)
            {
                ids.Add(authoring.ItemIds[i]);
            }

            Entity entity = GetEntity(TransformUsageFlags.Renderable);
            AddComponent(entity, new MyData{
                value = authoring.value
            });
        }
    }
}
public struct MyData : IComponentData
{
    public DynamicBuffer<int> ItemId;
    public int value;
}

I’m obviously using it incorrectly, as I get this error on MyData.ItemId:
ArgumentException: Blittable component type 'MyData' on GameObject 'Interactable' contains a (potentially nested) pointer field. Serializing bare pointers will likely lead to runtime errors. Remove this field and consider serializing the data it points to another way such as by using a BlobAssetReference or a [Serializable] ISharedComponent. If for whatever reason the pointer field should in fact be serialized, add the [ChunkSerializable] attribute to your type to bypass this error.

And this on ids.Add:
NullReferenceException: Object reference not set to an instance of an object

Will need to do more reading up on DynamicBuffer. It’s definitely what I need.

4

Dynamic Buffers are not fields in IComponentData. They are a buffer-like parallel to IComponentData, where each element is an IBufferElementData. You create one in a baker via AddBuffer().

1 Like
5

There’s also FixedList in Unity.Collections that you can put in an IComponentData.

6

You have to be very careful about this, because it breaks if the contained type has entity or blob ref fields.

1 Like