realm.io Retaining Child objects - copy

Question

So I'm using realm to cache and keep all data from our web-platform. which is loaded through an API.
When you fetch yourself as user we're also returning a user role, depending if you're a simple member, admin or whatever.
so it'd basically be
user: {
"username" : "user",
"role" : {"id":1,"name":"admin"}
}
which is cool, since realm stores this just fine in our objects which have the role as a child realmobject.
However when we load content, f/e comments. The object does not contain a role but it can contain the user which is current logged in. The data is being persisted and thus the role will be missing since it's not provided.
Are there any smart ways we could resolve this? or would the only option be to send role information with the user when comments are loaded.

Answer 1

If the username on User is defined as a primary key, you can use createOrUpdate / create(…, update: true) when retrieving the comments from the API to retain the user's role and merge it with the existing cached instance.
let realm = Realm()
let jsonDict = [
"message": "Hello world",
"user": [ "username" : "user" ]
]
realm.create(type: Comment.self, value: jsonDict, update: true)
Note that this works only as long as the role is missing from the retrieved JSON. If it's there as "role": null, the dictionary will contain a NSNull, which will cause that Realm nullifies the link from the user.