CODEWITHSUNDEEP
ioscore-datarestkitone-to-manyentity-relationship
LeffelMania
LeffelMania

Reputation: 12875

RestKit: Inverse Relationship Empty After Initial Mapping

Trying to connect two entities from my API from a single response. 

{
    "id": 4546,
    "body": "Direct message",
    "status": "received",
    "from": {
      "id": 723,
      "signature": "Mr. Whatever"
    },
    "sent_at": "2014-06-05T21:33:15Z",
    "sent_to": ...
  }

The object is a Message entity, the from field is a nested Sender entity. Here is the relevant relationship mapping:

RKEntityMapping *senderMapping = [RKEntityMapping mappingForEntityForName:@"Sender"
                                                          inManagedObjectStore:[AMModelManager sharedManager].managedObjectStore];

    senderMapping.identificationAttributes = @[ @"remoteId" ];
    [senderMapping addAttributeMappingsFromDictionary:@{
                                                         @"id" : @"remoteId",
                                                         @"signature" : @"signature"
                                                         }];

    [messageMapping addPropertyMapping:[RKRelationshipMapping relationshipMappingFromKeyPath:@"from"
                                                                                   toKeyPath:@"sender"
                                                                                 withMapping:senderMapping]];

The first time the objects are mapped, the relationship is not established. I see it being mapped in the log, but when I print any particular Sender object, its messages inverse relationship shows an empty array instead of a relationship fault.

Mapped relationship object from keyPath 'from' to 'sender'. Value: <Sender: 0x16a10990> (entity: Sender; id: 0x16a14580 <x-coredata:///Sender/t16539BDF-5606-442B-9EE2-D88363FB04AD29> ; data: {
    messages =     (
    );
    remoteId = 723;
    signature = "Mr. Whatever";
})

This makes the fetch requests I have in my application fail when I want to search for all messages from a given sender.

The next time I run the app and the mapping takes place again, all Message and Sender entities are remapped, the relationship is connected as expected, and my fetch requests behave as expected.

I really have no idea why the relationship isn't valid on the initial load. I don't know if it's a Core Data config issue or a RestKit issue, but it's driving me crazy and I would love any additional insight available. Glad to provide more information if necessary.

Edit

This is different than the proposed duplicate because this is a to-one relationship, so the proposed answer of using RKAssignmentPolicyUnion is inapplicable.

Update

Here is the fetch request I'm using for the controller I'm listening to:

NSFetchRequest *fetch = [NSFetchRequest fetchRequestWithEntityName:@"Sender"];
    fetch.predicate = [NSPredicate predicateWithFormat:@"SUBQUERY(SELF.messages, $message, $message.direct == %@).@count > 0 && SELF.remoteId != %@", @(YES), user.remoteId];
    fetch.sortDescriptors = @[
                              [NSSortDescriptor sortDescriptorWithKey:@"signature" ascending:YES selector:@selector(caseInsensitiveCompare:)]
                              ];

Semantically I'm trying to say "Give me all the Senders that have sent a Message directly to the current user, and who are not the current user, sorted by their signature."

This fetch request fetches the Sender objects that I expect when I run it after my data is retrieved, but the controller fires no updates and my table remains empty until the next time I run the application.

Upvotes: 1

Views: 353

Answers (1)

LeffelMania
LeffelMania

Reputation: 12875

K, another classic case of "You did it wrong and you were looking in all the wrong places to fix it."

I'd overridden the didChangeValueForKey: method on my Message entity's implementation to monitor some transient state, and neglected to call [super didChangeValueForKey:key], which fubar'd the inverse connection assignments in the mapping. Absolutely no issue with Core Data or RestKit. Just me being careless.

Upvotes: 2

Related Questions