Confused by the entity source

[hw762]

The documentation says ecs_field_src() can return 0 or some fixed source, in which case 0 means it->entities. What does it actually mean? If it->entities have multiple entries, do I index into them? What index if it always returns 0? How do I distinguish a fixed entity ID and an index?

[hw762]

I think I get it. What I get from it are tables, and it->entities have to be iterated anyways.