FetchRequest does not return NSManagedObjects fetched via RestKit 0.2

Question

I am having the following problem: I use RestKit to get objects form a REST Api. The object mapping works, which I can see from the RK Debugger Output. However, when I perform a fetch request afterwards, the result is empty. I am talking about NSManagedObjects. I have the following setup.

1: Restkit and Coredata stack initialization:

NSError *error;
NSURL *baseURL = [NSURL URLWithString:@"https://mfihost.us/gocoffee/api/V1/"];
RKObjectManager *objectManager = [RKObjectManager managerWithBaseURL:baseURL];
[objectManager.HTTPClient setDefaultHeader:@"Token" value:[NSString stringWithFormat:@"%@",[FBSDKAccessToken currentAccessToken].tokenString]];

objectManager.requestSerializationMIMEType = RKMIMETypeJSON;
[AFNetworkActivityIndicatorManager sharedManager].enabled = YES;
NSManagedObjectModel *managedObjectModel = [NSManagedObjectModel mergedModelFromBundles:nil];
RKManagedObjectStore *managedObjectStore = [[RKManagedObjectStore alloc] initWithManagedObjectModel:managedObjectModel];
objectManager.managedObjectStore = managedObjectStore;
//[RKObjectManager setSharedManager:objectManager];
[FetchRequests registerFetchRequests:objectManager];
[Descriptors registerDescriptors:objectManager];
[managedObjectStore createPersistentStoreCoordinator];
NSPersistentStore *persistentStore = [managedObjectStore addInMemoryPersistentStore:&error];
NSAssert(persistentStore, @"Failed to add inmemory store with error: %@", error);
[managedObjectStore createManagedObjectContexts];
managedObjectStore.managedObjectCache = [[RKInMemoryManagedObjectCache alloc] initWithManagedObjectContext:managedObjectStore.persistentStoreManagedObjectContext];

2: call to get objects from server and performing a fetch request afterwards:

[[RKObjectManager sharedManager]
     postObject:nil path:@"/gocoffee/api/V1/login/IOS"
     parameters:nil
     success: ^(RKObjectRequestOperation *operation, RKMappingResult *mappingResult) {
         NSLog(@"Objects have been saved in core data.");
         NSManagedObjectContext *managedObjCtx = [RKManagedObjectStore defaultStore].mainQueueManagedObjectContext;

        // Shout* sh=[managedObjCtx insertNewObjectForEntityForName:@"Shout"];
        // sh.inviterUserId=@"22223";

         NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
         NSEntityDescription *entity = [NSEntityDescription entityForName:@"Shout" inManagedObjectContext:managedObjCtx];
         [fetchRequest setEntity:entity];

         NSError *error = nil;
         NSArray *result = [managedObjCtx executeFetchRequest:fetchRequest error:&error];

         if (error) {
             NSLog(@"Unable to execute fetch request.");
             NSLog(@"%@, %@", error, error.localizedDescription);

         } else {
             NSLog(@"%@", result);
         }




         completionBlock();
     }
     failure: ^(RKObjectRequestOperation *operation, NSError *error) {
         RKLogError(@"Load failed with error: %@", error);
     }];

The fetch result is empty, although the server returns objects and these objects are properly mapped by using RKEntityMappings and the corresponding response descriptors. Confusingly, if I uncomment the two lines //Shout * .... (i.e. manually insert a managed oject into the context), then this object is fetched by the fetch request. Consequently, the fetch request should be working fine. I am searching for ages now what the problem might be. Could it be that I am calling on the wrong context or something ? By the way: core-data multi-threading debugging is enabled and does not show any error, i.e. no "AllThatIsLeftToUsIsHonor" error.

The corresponding route from the above example is:

[objectManager.router.routeSet
     addRoute:[RKRoute routeWithName:@"loginAndOrSignup"
                         pathPattern:@"login/IOS"
                              method:RKRequestMethodPOST]
     ];

The descriptors look like (example):

[objectManager addResponseDescriptor:
     [RKResponseDescriptor responseDescriptorWithMapping:[shoutMapping inverseMapping]
                                                  method:RKRequestMethodPOST
                                             pathPattern: @"login/IOS"
                                                 keyPath:@"response.incomingshoutapplications"
                                             statusCodes:RKStatusCodeIndexSetForClass(RKStatusCodeClassSuccessful)
      ]
     ];

Shout mapping is as follows:

RKEntityMapping *shoutMapping = [RKEntityMapping mappingForEntityForName:@"Shout" inManagedObjectStore:managedObjectStore];
    shoutMapping.identificationAttributes = @[ @"id" ];
    [shoutMapping addAttributeMappingsFromDictionary:@{
                                                       @"id" : @"id",
                                                       @"inviterUserId" : @"inviterUserId",
                                                       @"eventType" : @"eventType",
                                                       @"eventTime" : @"eventTime",
                                                       @"locationLat" : @"locationLat",
                                                       @"locationLng" : @"locationLng",
                                                       @"radius" : @"radius",
                                                       @"targetGender" : @"targetGender",
                                                       @"state" : @"state",
                                                       @"buddyOnly" : @"buddyOnly",
                                                       @"timeCreated" : @"timeCreated"
                                                       }
     ];

The "manager" ist the one from above, the managedObjectStore is manager.managedObjectStore All the mappings and descriptors are setup in another method that is calles by [Descriptors registerDescriptors:objectManager]; (see first block of code)

Answer 1

The problem is probably that you're using inverseMapping. That is used mainly for request mapping, because it's a mapping that creates instances of NSMutableDictionary, which isn't what you want.

So, what I expect is happening is that the response is mapped successfully, but to plain objects, not managed objects, and then you're throwing the result away.

Just change to

... responseDescriptorWithMapping:shoutMapping ...