Mapping relationships from JSON array with Restkit - ios

Question

I will try to be as descriptive as possible with this issue...
Scenario
Let's say i have a NSManagedObject 'User'
#class Premise;
#interface User : NSManagedObject
#property (nonatomic, retain) NSNumber * identifier;
#property (nonatomic, retain) NSString * name;
#property (nonatomic, retain) NSSet *premises;
#end
#interface User (CoreDataGeneratedAccessors)
- (void)addPremisesObject:(Premise *)value;
- (void)removePremisesObject:(Premise *)value;
- (void)addPremises:(NSSet *)values;
- (void)removePremises:(NSSet *)values;
#end
And i also have a NSManagedObject 'Premise'
#class User;
#interface Premise : NSManagedObject
#property (nonatomic, retain) NSNumber * identifier;
#property (nonatomic, retain) NSString * name;
#property (nonatomic, retain) User *user;
#end
Based on it, i am creating a relationship route to map a JSON array of 'Premise' to the 'premises' attribute on the 'User' object.
Here's the route:
let getPremisesRoute = RKRoute(relationshipName: "premises",
objectClass: User.self,
pathPattern: "user/:identifier/premises",
method: .GET)
Here's the JSON response (/user/1/premises):
[
{
"id": 35,
"name": "Icaraí"
},
{
"id": 32,
"name": "Remanso"
}
]
Here's the response descriptor:
let getPremisesResponseDescriptor = RKResponseDescriptor(mapping: premiseMapping, method: .GET, pathPattern: "user/:identifier/premises", keyPath: nil, statusCodes: RKStatusCodeIndexSetForClass(.Successful))
And here are the respective mappings of 'User' and 'Premise'
let userMapping = RKEntityMapping(forEntityForName: "User", inManagedObjectStore: moc)
userMapping.addAttributeMappingsFromDictionary(["id":"identifier", "name":"name"])
userMapping.identificationAttributes = ["identifier"]
userMapping.addPropertyMapping(RKRelationshipMapping(fromKeyPath: nil, toKeyPath: "premises", withMapping: premiseMapping))
let premiseMapping = RKEntityMapping(forEntityForName: "Premise", inManagedObjectStore: moc)
premiseMapping.addAttributeMappingsFromDictionary(["id":"identifier", "name":"name"])
premiseMapping.identificationAttributes = ["identifier"]
Now to my problem
Apparently, Restkit is getting a little bit confused during the mapping process. Here's the database after the request:
User Table:
Premise Table:
Note the the relationship is not being created between the entities.
Now, if I change the response descriptor's mapping from premise to user mapping, the database changes to this:
Users Table:
Premise Table:
I'm really confused on what's going on and I've tried a lot of solutions with no success.
Is the JSON response out of pattern or am I doing something wrong? The JSON response seems to be on a common pattern, with a nil key path.

Answer 1

You're approaching the mapping incorrectly, or at least your mappings are wrong for what you're doing. Consider that the response is a user, but only the premises for a user, instead of considering it as a simple list of premises as you are now. Then you map to a user and insert the premises. Something like:
RKResponseDescriptor(mapping: userMapping, method: .GET, pathPattern: "user/:identifier/premises", keyPath: nil, statusCodes: RKStatusCodeIndexSetForClass(.Successful))
And here are the respective mappings of 'User' and 'Premise'
let userMapping = RKEntityMapping(forEntityForName: "User", inManagedObjectStore: moc)
userMapping.addAttributeMappingsFromDictionary(["#metadata.routing.parameters.idEntities":"identifier"])
userMapping.identificationAttributes = ["identifier"]
userMapping.addPropertyMapping(RKRelationshipMapping(fromKeyPath: nil, toKeyPath: "premises", withMapping: premiseMapping))
let premiseMapping = RKEntityMapping(forEntityForName: "Premise", inManagedObjectStore: moc)
premiseMapping.addAttributeMappingsFromDictionary(["id":"identifier", "name":"name"])
premiseMapping.identificationAttributes = ["identifier"]
You don't have a user name in the response so you can't map it, and the user id is actually in the request so you need to use metadata to extract it.

Answer 2

Ok, I found a possible solution based on #Wain's solution using foreign keys.
I added a new property 'userID' to the 'Premise' entity and mapped it to the identifier on the URL using metadata
let premiseMapping = RKEntityMapping(forEntityForName: "Premise", inManagedObjectStore: moc)
premiseMapping.addAttributeMappingsFromDictionary(["id":"identifier", "name":"name", "#metadata.routing.parameters.identifier":"userID"])
Then I added a relationship connection to the 'premiseMapping'
premiseMapping.addConnectionForRelationship("user", connectedBy: ["userID":"identifier"])
If anyone has a more elegant solution please share with us.