Objective C + RESTKit: Problems with getting Objects - iphone

Question

I want to use RestKit for a Restful Webservice to communicate between an LAMP-environment and an iOS-App.
Therefore I made a first test to check out if it all works out like described in the tutorials available and on the RestKit page.
Right now the code looks like this:
RKObjectManager* objectManager = [RKObjectManager managerWithBaseURLString:#"http://localhost/resttest"];
objectManager.client.requestQueue.showsNetworkActivityIndicatorWhenBusy = YES;
#ifdef RESTKIT_GENERATE_SEED_DB
NSString *seedDatabaseName = nil;
NSString *databaseName = RKDefaultSeedDatabaseFileName;
#else
NSString *seedDatabaseName = RKDefaultSeedDatabaseFileName;
NSString *databaseName = #"CoreData.sqlite";
#endif
objectManager.objectStore = [RKManagedObjectStore objectStoreWithStoreFilename:databaseName usingSeedDatabaseName:seedDatabaseName managedObjectModel:nil delegate:self];
// Map Person Object
RKManagedObjectMapping *personMapping = [RKManagedObjectMapping mappingForClass:[Person class] inManagedObjectStore:objectManager.objectStore];
//RKManagedObjectMapping *personMapping = [RKManagedObjectMapping mappingForEntityWithName:#"Person" inManagedObjectStore:[RKObjectManager sharedManager].objectStore];
[personMapping mapKeyPath:#"id" toAttribute:#"person_id"];
[personMapping mapKeyPath:#"firstname" toAttribute:#"person_firstname"];
[personMapping mapKeyPath:#"lastname" toAttribute:#"person_lastname"];
[personMapping mapKeyPath:#"gender" toAttribute:#"person_gender"];
personMapping.primaryKeyAttribute = #"id";
// Register our mappings with the provider;
[objectManager.mappingProvider setMapping:personMapping forKeyPath:#"/person"];
objectManager.acceptMIMEType = RKMIMETypeJSON;
#ifdef RESTKIT_GENERATE_SEED_DB
RKLogConfigureByName("RestKit/ObjectMapping", RKLogLevelInfo);
RKLogConfigureByName("RestKit/CoreData", RKLogLevelTrace);
#endif
[objectManager loadObjectsAtResourcePath:#"/person" delegate:self];
This is how my Managed Object looks like:
#interface Person : NSManagedObject
#property (nonatomic, retain) NSString * person_firstname;
#property (nonatomic, retain) NSString * person_lastname;
#property (nonatomic, retain) NSString * person_gender;
#property (nonatomic, retain) NSNumber * person_id;
#end
And this is the dummy-code on server side which only returns some json example string:
<?php
header('Content-type: application/json');
if($_SERVER['REQUEST_METHOD'] == 'GET')
{
$json_string = '{ "persons": [
{ "id": "1",
"firstname": "hans",
"lastname": "maier",
"genre": "m"
},
{ "id": "2",
"firstname": "michael",
"lastname": "schmidt",
"genre": "w"
}]
}';
echo $json_string;
}
?>
The URI to get the returned json-String is http://localhost/resttest/person(/index.php).
My problems are:
I always get this Error when i don't define a resource path for '':
E restkit.network:RKObjectLoader.m:216 Encountered errors during mapping: Could not find an object mapping for keyPath: ''
and I don't know why this happens. No other example I tried has this problem, but I don't have a clue what I'm doing wrong.
When it works (I have to change the Base URL to http://localhost/resttest/person), I get an empty object instead of an error.
I would appreciate any help on this topic, because right now i don't know what I'm doing wrong.
Thank you!
Edit 03.05.2012:
Here is what i get in the logs:
2012-05-03 12:52:05.067 RESTKitCoreDataTest[5139:13807] D restkit.object_mapping:RKObjectMapper.m:320 Performing object mapping sourceObject: {
persons = (
{
firstname = hans;
gender = m;
id = 1;
lastname = maier;
},
{
firstname = michael;
gender = w;
id = 2;
lastname = schmidt;
}
);
}
and targetObject: (null)
2012-05-03 12:52:05.067 RESTKitCoreDataTest[5139:13807] T restkit.object_mapping:RKObjectMapper.m:278 Examining keyPath '' for mappable content...
2012-05-03 12:52:05.067 RESTKitCoreDataTest[5139:13807] D restkit.object_mapping:RKObjectMapper.m:264 Found mappable data at keyPath '': {
persons = (
{
firstname = hans;
gender = m;
id = 1;
lastname = maier;
},
{
firstname = michael;
gender = w;
id = 2;
lastname = schmidt;
}
);
}
2012-05-03 12:52:05.073 RESTKitCoreDataTest[5139:13807] D restkit.object_mapping:RKObjectMapper.m:210 Asked to map source object {
persons = (
{
firstname = hans;
gender = m;
id = 1;
lastname = maier;
},
{
firstname = michael;
gender = w;
id = 2;
lastname = schmidt;
}
);
} with mapping <RKManagedObjectMapping:0x811eb60 objectClass=Person keyPath mappings => (
"RKObjectKeyPathMapping: id => person_id",
"RKObjectKeyPathMapping: firstname => person_firstname",
"RKObjectKeyPathMapping: lastname => person_lastname",
"RKObjectKeyPathMapping: gender => person_gender"
)>
2012-05-03 12:52:05.074 RESTKitCoreDataTest[5139:13807] D restkit.object_mapping:RKObjectMappingOperation.m:617 Starting mapping operation...
2012-05-03 12:52:05.074 RESTKitCoreDataTest[5139:13807] T restkit.object_mapping:RKObjectMappingOperation.m:618 Performing mapping operation: RKObjectMappingOperation for 'Person' object. Mapping values from object {
persons = (
{
firstname = hans;
gender = m;
id = 1;
lastname = maier;
},
{
firstname = michael;
gender = w;
id = 2;
lastname = schmidt;
}
);
} to object <Person: 0x6e295d0> (entity: Person; id: 0x6e29610 <x-coredata:///Person/t99EFF6DC-EBDA-405C-8AFF-D082E4A8542F2> ; data: {
"person_firstname" = nil;
"person_gender" = nil;
"person_id" = 0;
"person_lastname" = nil;
}) with object mapping <RKManagedObjectMapping:0x811eb60 objectClass=Person keyPath mappings => (
"RKObjectKeyPathMapping: id => person_id",
"RKObjectKeyPathMapping: firstname => person_firstname",
"RKObjectKeyPathMapping: lastname => person_lastname",
"RKObjectKeyPathMapping: gender => person_gender"
)>
2012-05-03 12:52:05.074 RESTKitCoreDataTest[5139:13807] T restkit.object_mapping:RKObjectMappingOperation.m:388 Did not find mappable attribute value keyPath 'id'
2012-05-03 12:52:05.074 RESTKitCoreDataTest[5139:13807] T restkit.object_mapping:RKObjectMappingOperation.m:388 Did not find mappable attribute value keyPath 'firstname'
2012-05-03 12:52:05.075 RESTKitCoreDataTest[5139:13807] T restkit.object_mapping:RKObjectMappingOperation.m:388 Did not find mappable attribute value keyPath 'lastname'
2012-05-03 12:52:05.075 RESTKitCoreDataTest[5139:13807] T restkit.object_mapping:RKObjectMappingOperation.m:388 Did not find mappable attribute value keyPath 'gender'
2012-05-03 12:52:05.075 RESTKitCoreDataTest[5139:13807] D restkit.object_mapping:RKObjectMappingOperation.m:638 Mapping operation did not find any mappable content
2012-05-03 12:52:05.075 RESTKitCoreDataTest[5139:13807] T restkit.core_data:RKManagedObjectMappingOperation.m:98 relationshipsAndPrimaryKeyAttributes: {
}
2012-05-03 12:52:05.075 RESTKitCoreDataTest[5139:13807] D restkit.object_mapping:RKObjectMapper.m:351 The following operations are in the queue: (
)
2012-05-03 12:52:05.075 RESTKitCoreDataTest[5139:13807] D restkit.object_mapping:RKObjectMapper.m:366 Finished performing object mapping. Results: {
}
2012-05-03 12:52:05.080 RESTKitCoreDataTest[5139:fb03] Loaded persons: (
)

Answer 1

Possibility 1:
It seems that your setting the mapping to the wrong keypath.
Try
// Register our mappings with the provider;
[objectManager.mappingProvider setMapping:personMapping forKeyPath:#"persons"];
and check if it works.
Possibility 2:
Specify the root path of your JSON in your mapping.
Try
// Map Person Object
RKManagedObjectMapping *personMapping = [RKManagedObjectMapping mappingForClass:[Person class] inManagedObjectStore:objectManager.objectStore];
[personMapping mapKeyPath:#"id" toAttribute:#"person_id"];
[personMapping mapKeyPath:#"firstname" toAttribute:#"person_firstname"];
[personMapping mapKeyPath:#"lastname" toAttribute:#"person_lastname"];
[personMapping mapKeyPath:#"gender" toAttribute:#"person_gender"];
personMapping.rootKeyPath = #"persons";
personMapping.primaryKeyAttribute = #"id";
and check if it works.