How to parse JSON to an entity that has a relationship to itself using Sync? - ios

Question

I am using Sync trying to parse some JSON to Core Data.
My "Creature" entity has a parent-children relationship that looks like this:
and the JSON has a format similar to this:
[
{
"id": 1,
"name": "Mad king",
"parent": null,
"children": [
5
]
},
{
"id": 2,
"name": "Drogon",
"parent": 5,
"children": []
},
{
"id": 3,
"name": "Rhaegal",
"parent": 5,
"children": []
},
{
"id": 4,
"name": "Viserion",
"parent": 5,
"children": []
},
{
"id": 5,
"name": "Daenerys",
"parent": 1,
"children": [
2,
3,
4
]
}
]
The Mad king has one child Daenerys who has 3 children (Drogon, Rhaegal and Viserion).
Now, I know that Sync does support this sort of setup (where the JSON contains only the ids of parents/children instead of whole objects) and I suspect I have to parse the file twice - one for just getting all the objects and the second to create the relationships among them. For the second to work, I need to rename children to children_ids and parent to parent_id (as described in their README).
However I can't understand how exactly would I do that. Is it possible to ignore the parent/children during the first pass and then take them into account (using the modified keys) during the second?
Or could someone maybe propose a better solution that would (ideally) require just one pass?

Answer 1

According to the documentation:
For example, in the one-to-many example, you have a user, that has
many notes. If you already have synced all the notes then your JSON
would only need the notes_ids, this can be an array of strings or
integers. As a side-note only do this if you are 100% sure that all
the required items (notes) have been synced, otherwise this
relationships will get ignored and an error will be logged.
So you can, in theory, just blindly perform a full sync to actually get all the models(letting it fail on the relationships), and then sync again immediately after to get the relationships.
If you want to avoid the errors, you might want to write some helper functions to create 2 sets of JSON for these models, 1 to define the objects, and then a second to define the relationships. Either way, you'd need to do 2 passes.