Referencing other entities

[frankiesardo]

I apologise if it's just me, but by reading the docs it's not very clear how to reference other entities inside datascript.

[
 {:db/id -10
  :name "C1"
  :value "foo"} 
 {:db/id -11
  :name "C2"
  :value "bar"}      
 {:db/id -1
  :name  "E"
  :components [-10, -11]}
]

How do I reference the generated ids 10 and 11 inside the components vector?

[tonsky]

Yeah, I forgot about that case :( Maybe we should go with something like Datomic’s tempids or deduce value type from schema. Will think of something for the next version

[yusefnapora]

Have you given this any more thought? It seems like specifying the value type in the schema has the advantage that you could return referenced entities in the d/entity function, similar to Datomic. So, in frankiesardo's example, you could do

(def e (d/entity db 1))
(get-in e [:components 0 :name]) ; => "foo"

Of course, d/entity would have to be rewritten to support that. But it seems like for that to be possible, you would want the type to be in the schema.

[tonsky]

I’ll probably go with the schema, and leave negative ids as they works right now, without tempid wrapper. Entity to follow references is a little bit harder because there may be cycles so we need lazy entities for this to work properly. It’s on the roadmap, but not on the closest one.

[tonsky]

Check out test.datascript/test-resolve-eid-refs for usage example