RestKit 0.20: Relational map data from a local file

Question

I take a local JSON file and try to map it to a relational mapping. It works fine without a relationship, but as soon as I add a relationship, I get an error.

JSON:

https://gist.github.com/4675414

Code:

// Get json from destination NSString *myJSON = [[NSString alloc] initWithContentsOfFile:contentPath encoding:NSUTF8StringEncoding error:NULL]; NSString* MIMEType = @"application/json"; NSError* parseError; NSData *data = [myJSON dataUsingEncoding:NSUTF8StringEncoding]; id parsedData = [RKMIMETypeSerialization objectFromData:data MIMEType:MIMEType error:&parseError]; if (parsedData == nil && parseError) { NSLog(@"Cannot parse data: %@", parseError); } // Setting up objectmapping for issue RKObjectMapping *issueMapping = [RKObjectMapping mappingForClass:[Issue class]]; [issueMapping addAttributeMappingsFromDictionary:@{ @"title": @"title", @"description": @"description", @"cover_url": @"cover_url", @"published_at": @"published_at", @"issue_number": @"issue_number" }]; //Setting up objectmapping for article RKObjectMapping *articleMapping = [RKObjectMapping mappingForClass:[Article class]]; [articleMapping addAttributeMappingsFromDictionary:@{ @"title": @"title", @"main_text": @"main_text", @"article_image_url": @"article_image_url" }]; [issueMapping addPropertyMapping:[RKRelationshipMapping relationshipMappingFromKeyPath:@"articles" toKeyPath:@"articles" withMapping:articleMapping]]; Issue *issue = [[Issue alloc] init]; RKMappingOperation* mapper = [[RKMappingOperation alloc] initWithSourceObject:[parsedData objectForKey:@"issue"] destinationObject:issue mapping:issueMapping]; RKManagedObjectMappingOperationDataSource *mappingDS = [RKManagedObjectMappingOperationDataSource new]; mapper.dataSource = mappingDS; [mapper performMapping:&parseError]; NSLog(@"Parse error: %@", parseError); NSLog(@"Issue title: %@", issue.title); 

Error:

  2013-01-30 13:07:42.486 uninkd[13722:907] *** Assertion failure in -[RKManagedObjectMappingOperationDataSource mappingOperation:targetObjectForRepresentation:withMapping:inRelationship:], /Users/holgersindbaek/Projects/Uninkd/Uninkd_IOS/Pods/RestKit/Code/CoreData/RKManagedObjectMappingOperationDataSource.m:232 2013-01-30 13:07:42.487 uninkd[13722:907] *** Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'RKManagedObjectMappingOperationDataSource must be initialized with a managed object context.' 

Error if I take the data source:

  2013-01-30 13:27:32.601 uninkd[13754:907] *** Assertion failure in -[RKMappingOperation applyRelationshipMappings], /Users/holgersindbaek/Projects/Uninkd/Uninkd_IOS/Pods/RestKit/Code/ObjectMapping/RKMappingOperation.m:699 2013-01-30 13:27:32.603 uninkd[13754:907] *** Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'Cannot perform relationship mapping without a data source' 

Hope you can help.

Answer 1

This is due to the fact that RKManagedObjectMappingOperationDataSource expects a managed object context, this is specifically for Core Data. Do you use master data?

Forget everything I said earlier and use:

 #import "RKObjectMappingOperationDataSource.h" RKObjectMappingOperationDataSource *mappingDS = [RKObjectMappingOperationDataSource new]; mapper.dataSource = mappingDS; 

instead:

 RKManagedObjectMappingOperationDataSource *mappingDS = [RKManagedObjectMappingOperationDataSource new]; mapper.dataSource = mappingDS; 

Hint, don't use classes that say ManagedObject unless you are using CoreData. This applies to ManagedObject in ManagedObjectContext , which is unique to CoreData. That being said, core data + restkit is awesome and you should check it out.