I have another noob question 🙂

Do you use :db.type/ref in your actual code? Or do you just look up by properties?

The reason I’m asking is that I’m currently playing with an existing API to our app

We have the following entities:

A city: {cityId: xxx, name: "Something"}
A venue: {venueId: yyy, name: "Something", cityId: xxx}
An event: {eventId: zzz, name: "Something", venueId: yyy}

How do you mean? We use refs in schema. Do you mean do we dynamically analyse our schema?

Let’s say I want to have an event referencing a venue referencing a city

I tried to do that by setting :db/id to *Id, but, obviously, venue with :db/id set to 1 would get overwritten by event with :db/id set to 1

🙂

what

🙂

I don’t see a problem in your data

cityId and venueId could totally be refs

they should be refs

I just realized how to solve this 😄 I think.

- If we display a list of cities, we know their entities. - Click on city, load venues for that city. - On load, set :venue/city (or whatever) to the currently (:db/id (currently-selected-city))

are you sure you’re talking about datascript?

Yes 🙂

The thing is: the API is an existing API, so it’s not Datascript-optimized.

so you want to keep original ids?

So what I get from the server is:

Cities: [{cityId: 1, name: "Stockholm"}, {cityId: 2, "Copenhagen"}]
// click Stokcholm get:
Venues: [{venueId: 1, name: "Berns", cityId: 1}, {venueId: 2, "Ambassador", cityId: 1}}]
// Click Berns get
Events: [{eventId: 2, name: "Party!", venueId: 1} ...]

So it’s kinda “I want to keep original ids and use refs” 🙂

you’ll need to use “external id” attributes for those

but for refs you’ll need to use datascript ids

[{ :cityId 1, :name "Stockholm"}
 { :cityId 2, :name "Copenhagen"}
 { :venueId 1, :name "Berns", :city [:cityId 1] }]

a-ha!

and you’ll need to mark :cityId :venueId as :db.unique/identity and :city as ref

I’ll have to try this 🙂

then [:cityId 1] will be resolved to datascript id of entity that has :cityId attribute set to 1

nice!

yeah. Feature is called “lookup refs”

basically it’s nothing more but a nice syntax to find entity id by attribute and value

I’ll still need to massage incoming data a little, but it’s still awesome!

So little time, so much to learn 🙂

Thanks!