How can I set same primary key in nested RLMObject with RKObjectMapping?

Question

I want to set same primary key in nested RLMObject.
How can I set same id with RKObjectMapping?

firstly, I made following json file.
JSON file

{
  "id": 1
  "obj2": {
    "name": "name1"  
  } 
}

Secondly, I make following swift class file.
Class file

class Obj2: RLMObject {
    dynamic var id: Int <-- I want to set same id as Obj1.id
    dynamic var name: String!

    override class func primaryKey() -> String {
        return "id"
    }

    class func responseMapping() -> RKObjectMapping {
        let objectMapping = RKObjectMapping(forClass: self)
        objectMapping.addAttributeMappingsFromDictionary([
            "name": "name"
        return objectMapping
    }
}

class Obj1: RLMObject {
    dynamic var id: Int!
    dynamic var obj2: Obj2?

    override class func primaryKey() -> String {
        return "id"
    }

    class func responseMapping() -> RKObjectMapping {
        let objectMapping = RKObjectMapping(forClass: self)
        objectMapping.addAttributeMappingsFromDictionary([
            "id": "id"

        objectMapping.addPropertyMappingsFromArray([
            RKRelationshipMapping(fromKeyPath: "obj2", toKeyPath: "obj2", withMapping: Obj2.responseMapping())
        ])

        return objectMapping
    }
}

Answer 1

You would need to setup your mapping on the same JSON base object and not traverse the scope, which would make the mapping dependent on the relation.

class Obj2: RLMObject {
    dynamic var id: Int
    dynamic var name: String!

    override class func primaryKey() -> String {
        return "id"
    }

    class func responseMappingForBeingOwnedByObj1() -> RKObjectMapping {
        let objectMapping = RKObjectMapping(forClass: self)
        objectMapping.addAttributeMappingsFromDictionary([
            "id": "id",
            "name": "obj2.name"
        ])
        return objectMapping
    }
}

class Obj1: RLMObject {
    dynamic var id: Int!
    dynamic var obj2: Obj2?

    override class func primaryKey() -> String {
        return "id"
    }

    class func responseMapping() -> RKObjectMapping {
        let objectMapping = RKObjectMapping(forClass: self)
        objectMapping.addAttributeMappingsFromDictionary([
            "id": "id"
        ])

        objectMapping.addPropertyMappingsFromArray([
            RKRelationshipMapping(fromKeyPath: ".", toKeyPath: "obj2", withMapping: Obj2.responseMappingForBeingOwnedByObj1())
        ])

        return objectMapping
    }
}

Some last words of warning: RestKit doesn't really support Realm at this point. So you may be better off with using something else for now, e.g. Realm's limited built-in support for decoding object representations, Realm+JSON or Decodable.