Important ECS Info.md

Requirements for a working entity component

An IComponentData implementation must be a struct and can only contain unmanaged, blittable types, including:

• C#-defined blittable types
• bool
• char
• BlobAssetReference<T> (a reference to a Blob data structure)
• FixedString (a fixed-sized character buffer)
• Unity.Collections.FixedList
• fixed arrays (in an unsafe context)
• structs containing these unmanaged, blittable fields

Further reading at Unity's documentation on IComponentData.

Using ints as an example of a simple blittable value.

Examples:

• Blittable values

public struct someCustomComponent : IComponentData
{
    //example variables shown here barely scratches the surface of what's allowed.
    public int integer;
    public int2 integer2;
    public int2x2 integer2x2;
    public int4 integer4;
    public int4x2 integer4x2;
    public int4x4 integer4x4;

    //No pre-assignment is permitted
    public int preassigned_int = 333;
}

• Unallowed in unmanaged IComponentData:

public struct someCustomComponent : IComponentData
{
    //Resizeable structs and/or arrays are not allowed
    public int[] intArray;
    public List<int> intList;
    public Dictionary<key, int> intDictionary;
    public NativeArray<int> intNativeArray;
    public NativeList<int> intNativeList;
    public NativeSlice<int> intNativeSlice;
    public DynamicBuffer<int> intDynamicBuffer;

    //References are not allowed
    public anyClass classObject;
    public object objectReference;
}