Realm inverse-relationships support for creation with a dictionary value

Question

I'd like to implement Realm inverse-relationships support for creation with a dictionary.

But the assertion fails: the dog from the dictionary was not created.

import RealmSwift

class Dog: Object {
    dynamic var name: String?
    dynamic var owner: Person?
}

class Person: Object {
    dynamic var name: String?
    let dogs = LinkingObjects(fromType: Dog.self, property: "owner")
}

func sample() -> Person? {
    // Get the default Realm
    let realm = try? Realm()

    let sampleValue: [String: Any] = ["name": "Harry", "dogs": [["name": "Belle"]]]
    var person: Person? = nil
    try? realm?.write {
        person = realm?.create(Person.self, value: sampleValue, update: false)
    }

    assert(person?.dogs.isEmpty == false)

    return person
}

Note: RealmSwift (2.1.2)

Answer 1

LinkingObjects is a lookup mechanism, and not an actual representation of an on-disk store. As such, it's not possible to insert data into it via a write transaction.

However, if you redesign your schema, so Person has a List of Dog objects, and Dog itself defines a LinkingObjects to determine its parents, then your code of inserting a Person and Dog in the same dictionary should work. :)

class Dog: Object {
    dynamic var name: String?
    let owners = LinkingObjects(fromType: Person.self, property: "dogs")
}

class Person: Object {
    dynamic var name: String?
    let dogs = List<Dog>()
}

Answer 2

Workaround I found was to create each entity separately.

try? realm.write {
    person = realm.create(Person.self, value: sampleValue, update: false)
    let dogsValue = sampleValue["dogs"] as? [[String: Any]]
    dogsValue?.forEach {
        var dogValue = $0
        dogValue["owner"] = person
        realm.create(Dog.self, value: dogValue, update: false)
    }
}

I hope there are some easier ways.