Manually load objects using RestKit into Core Data using JSON string - iphone

Question

Using the development branch of restkit (0.20), is there a way to perform mapping on a JSON string into the core data object store?
I know in 0.10, the method described at the bottom of this page worked but how is this operation performed in restkit 0.20? Any guidance appreciated! Thanks!
id<RKParser> parser = [[RKParserRegistry sharedRegistry] parserForMIMEType:MIMEType];
id parsedData = [parser objectFromString:JSONString error:&error];
RKObjectMappingProvider* mappingProvider = [RKObjectManager sharedManager].mappingProvider;
RKObjectMapper* mapper = [RKObjectMapper mapperWithObject:parsedData mappingProvider:mappingProvider];
RKObjectMappingResult* result = [mapper performMapping];

Answer 1

I installed RESTKit v0.20.0pre4 yesterday and had the same need for one particular case.
Here is an example of the JSON String I want to map:
{"info":"the sun is shining","detail":"in Bordeaux ~ 29 °C"}
This is how I perform the mapping.
- (InfoRESTMapped *)mapInfoFromJSONString:(NSString *) JSONString{
NSString* MIMEType = #"application/json";
NSError* error;
NSData *data = [JSONString dataUsingEncoding:NSUTF8StringEncoding];
id parsedData = [RKMIMETypeSerialization objectFromData:data MIMEType:MIMEType error:&error];
if (parsedData == nil && error) {
//deal with error
}
RKObjectMapping *infoMapping = [RKObjectMapping requestMapping];
[infoMapping addAttributeMappingsFromDictionary:#{
#"info": #"myInfo",
#"detail": #"myDetail",
}];
InfoRESTMapped *infoMapped = [[InfoRESTMapped alloc] init];
RKMappingOperation* mapper = [[RKMappingOperation alloc] initWithSourceObject:parsedData destinationObject:infoMapped mapping:infoMapping];
[mapper performMapping:&error];
return infoMapped;
}
These posts led me to the solution I have suggested:
https://github.com/RestKit/RestKit/issues/999
https://groups.google.com/d/topic/restkit/M1d7WwcFBDA/discussion
I hope it helps. I guess some other will give better solutions when the final version will be released (with better documentation too...).

Answer 2

For Restkit 0.22, You can use this code. This returns an RKMappingResult wherein you can enumerate the objects after mapping using the property .array.
- (RKMappingResult *)mapJSONStringWithString:(NSString *)jsonString
{
RKMappingResult *result = nil;
NSError* error;
NSData *data = [jsonString dataUsingEncoding:NSUTF8StringEncoding];
id parsedData = [RKMIMETypeSerialization objectFromData:data MIMEType:RKMIMETypeJSON error:&error];
if (parsedData == nil && error) {
NSLog(#"json mapping error");
}
NSDictionary *mappingsDictionary = #{#"":[CustomMappingClass getMappingForUsers]};
ObjectClass *obj = [ObjectClass new];
RKMapperOperation *mapper = [[RKMapperOperation alloc] initWithRepresentation:parsedData mappingsDictionary:mappingsDictionary];
NSError *mappingError = nil;
mapper.targetObject = obj;
BOOL isMapped = [mapper execute:&mappingError];
if (isMapped && !mappingError) {
result = [mapper mappingResult];
}
return result;
}

Answer 3

The most straightforward way to import JSON into your Core Data store using RestKit is documented in the Read Me "Generate a Seed Database"
Here is what I wrote in Swift:
if let persistentStore = RKManagedObjectStore.default().persistentStoreCoordinator.persistentStores.first {
if let objectImporter = RKManagedObjectImporter.init(persistentStore: persistentStore) {
let path = Bundle.main.path(forResource: jsonFile, ofType: "json")
let mapping = SLTour.responseMapping()
var error:NSError?
objectImporter.importObjectsFromItem(atPath: path, with: mapping, keyPath: "data", error: &error)
try objectImporter.finishImporting()
objectImporter.logSeedingInfo()
}
}
Hopefully, this will save somebody from several hours of trying to solve this in the future.