Restkit mapping issue - post newly created managed object to the server - core-data

Question

I'm trying to post new managed object to the server by using rest kit, but I don't know what I'm doing wrong. I'm getting exception like the following:
Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: 'RKRequestDescriptor objects must be initialized with a mapping whose target class is NSMutableDictionary, got 'Users' (see [RKObjectMapping requestMapping])'
I was looking for solution in stack overflow posts like this one
This is my entity mapping method from MappingProvider class:
+(RKMapping *)usersMapping
{
RKEntityMapping *mapping = [RKEntityMapping mappingForEntityForName:#"Users" inManagedObjectStore:[[DateModel sharedDataModel]objectStore]];
[mapping addAttributeMappingsFromDictionary:#{
#"id": #"user_id",
#"address1": #"address1",
#"address2": #"address2",
#"created_at":#"created_at",
#"updated_at": #"updated_at",
#"email": #"email",
#"name":#"name",
#"password_digest": #"password_digest",
#"phone_no": #"phone_no",
#"postcode":#"postcode",
#"remember_token":#"remember_token",
#"user_type": #"user_type",
#"apns_token":#"apns_token"
}
];
[mapping addRelationshipMappingWithSourceKeyPath:#"admins" mapping:[MappingProvider adminsMapping]];
[mapping addRelationshipMappingWithSourceKeyPath:#"carers" mapping:[MappingProvider carersMapping]];
[mapping addRelationshipMappingWithSourceKeyPath:#"customers" mapping:[MappingProvider customersMapping]];
[mapping addRelationshipMappingWithSourceKeyPath:#"userWearers" mapping:[MappingProvider customersMapping]];
return mapping;
This is the method called when user fill all the textfields and click the register button:
-(void)registerUser
{RKResponseDescriptor *userResponseDescriptor = [RKResponseDescriptor responseDescriptorWithMapping:[MappingProvider usersMapping] method:RKRequestMethodPOST pathPattern:nil keyPath:nil statusCodes:RKStatusCodeIndexSetForClass(RKStatusCodeClassSuccessful)];
//here Xcode return exception
RKRequestDescriptor *requestDescriptor = [RKRequestDescriptor requestDescriptorWithMapping:[MappingProvider usersMapping] objectClass:[Users class] rootKeyPath:nil method:RKRequestMethodPOST];
[[DateModel sharedDataModel]addResponseDescriptor:userResponseDescriptor];
[[DateModel sharedDataModel]addRequestDescriptor:requestDescriptor];
RKManagedObjectStore *objectStore = [[DateModel sharedDataModel]objectStore];
Users *user = [NSEntityDescription insertNewObjectForEntityForName:#"Users" inManagedObjectContext:objectStore.mainQueueManagedObjectContext];
user.email = _email;
user.password_digest =_password;
user.name = _name;
user.address1 = _address;
user.postcode = [NSNumber numberWithInteger:[_postcode integerValue]];
user.phone_no = [NSNumber numberWithInteger:[_mobileNumber integerValue]];
[[RKObjectManager sharedManager] postObject:user path:nil parameters:nil success:^(RKObjectRequestOperation *operation, RKMappingResult *mappingResult) {
NSLog(#"Success saving user");
} failure:^(RKObjectRequestOperation *operation, NSError *error) {
NSLog(#"Failure saving user: %#", error.localizedDescription);
}];
}
Date-model setup method:
- (void)setup {
self.objectStore = [[RKManagedObjectStore alloc] initWithManagedObjectModel:[self managedObjectModel]];
NSString *path = [RKApplicationDataDirectory() stringByAppendingPathComponent:#"Data.sqlite"];
NSLog(#"Setting up store at %#", path);
[self.objectStore addSQLitePersistentStoreAtPath:path
fromSeedDatabaseAtPath:nil
withConfiguration:nil
options:[self optionsForSqliteStore]
error:nil];
[self.objectStore createManagedObjectContexts];
//Configure a managed object cache to ensure we do not create duplicate objects
self.objectStore.managedObjectCache =[[RKInMemoryManagedObjectCache alloc]initWithManagedObjectContext:self.objectStore.persistentStoreManagedObjectContext];
// Set the default store shared instance
[RKManagedObjectStore setDefaultStore:self.objectStore];
}

Answer 1

The purpose of the request descriptor is to convert your custom object into an NSMutableDictionary so that it can be serialised and sent. The mapping you're currently using is for converting into a Users object, so you need to use a different mapping.
RestKit has a convenience method that you can use:
... requestDescriptorWithMapping:[[MappingProvider usersMapping] inverseMapping] ...