RestKit: no se pudo encontrar una asignación de object para keyPath: ''

El siguiente código produce este error.

- (void)viewDidLoad { RKObjectManager * manager = [RKObjectManager objectManagerWithBaseURLString:@"http://localhost:3000"]; RKObjectMapping *contactMapping = [RKObjectMapping mappingForClass:[Contact class]]; [contactMapping mapKeyPathsToAttributes: @"nom", @"nom", @"prenom", @"prenom", @"telephone", @"telephone", @"commentairs", @"description", nil]; [manager.mappingProvider setMapping:contactMapping forKeyPath:@"/contacts.json"]; [manager loadObjectsAtResourcePath:@"/contacts.json" delegate:self]; } 

No sé cómo emparejar la ruta de resources con la asignación. Alguna idea ?

Los loggings son:

 2012-09-18 11:07:30.811 MyApp[28507:fb03] I restkit:RKLog.m:33 RestKit initialized... 2012-09-18 11:07:30.816 MyApp[28507:fb03] mapping : <RKObjectMappingProvider: 0x6c1c860> 2012-09-18 11:07:30.837 MyApp[28507:fb03] I restkit.network.reachability:RKReachabilityObserver.m:391 Network availability has been determined for reachability observer <RKReachabilityObserver: 0x6c51e60 host=localhost isReachabilityDetermined=YES isMonitoringLocalWiFi=NO reachabilityFlags=-R -----l-> 2012-09-18 11:07:30.886 MyApp[28507:fb03] I restkit.network:RKRequest.m:680 Updating cache date for request <RKObjectLoader: 0x6c54ec0> to 2012-09-18 11:07:30 +0000 2012-09-18 11:07:30.892 MyApp[28507:11503] W restkit.object_mapping:RKObjectMapper.m:87 Adding mapping error: Could not find an object mapping for keyPath: '' 2012-09-18 11:07:30.893 MyApp[28507:11503] E restkit.network:RKObjectLoader.m:231 Encountenetworking errors during mapping: Could not find an object mapping for keyPath: '' 2012-09-18 11:07:30.914 MyApp[28507:fb03] Error : [didFailWithError] 

Y la respuesta json es la siguiente (proviene de una Ruby on Rails Rest API):

 [ {"commentairs":"bla bla", "created_at":"2012-09-17T21:15:55Z","id":1, "nom":"name 1", "prenom":"surname A", "telephone":"+33687330913", "updated_at":"2012-09-17T21:22:34Z"}, {"commentairs":"bla bla", "created_at":"2012-09-17T21:22:20Z","id":2, "nom":"name 2", "prenom":"surname 2", "telephone":"", "updated_at":"2012-09-17T21:22:20Z"} ] 

KeyPath no es el nombre de su file json, sino el punto de partida para RestKit:

 { "contact": { "nom": "whatever nom is", "prenom": "same for prenom", // ... } // ... } 

En este caso, "contacto" sería su keyPath: [manager.mappingProvider setMapping:contactMapping forKeyPath:@"contact"];