 <p>I usually add the <code>RKObjectMapping</code> to the managedObject class</p> <p>Add this to your Document.h</p> <pre><code> + (RKObjectMapping *)objectMapping; </code></pre> <p>Add this method to your Document.m</p> <pre><code>+ (RKObjectMapping *)objectMapping { RKManagedObjectMapping *mapping = [RKManagedObjectMapping mappingForClass:[self class] inManagedObjectStore:[[RKObjectManager sharedManager] objectStore]]; mapping.primaryKeyAttribute = @"word"; [mapping mapKeyPath:@"word" toAttribute:@"word"]; [mapping mapKeyPath:@"min_lesson" toAttribute:@"minLesson"]; </code></pre> <p>} </p> <p>Off course you should change the key paths to your Document object properties. each pair is the name of the key on the server responds and it's corresponded keyPath on your managedObject.</p> <p>Then when you initialize the <code>objectManager</code> you can set the mapping for each managedObject you have.</p> <pre><code> RKManagedObjectStore *store = [RKManagedObjectStore objectStoreWithStoreFilename:databaseName usingSeedDatabaseName:seedDatabaseName managedObjectModel:nil delegate:self]; objectManager.objectStore = store; //set the mapping object from your Document class [objectManager.mappingProvider setMapping:[SRLetter objectMapping] forKeyPath:@"Document"]; </code></pre> <p>YOu can find a great tutorial here - <a href="http://mobile.tutsplus.com/tutorials/iphone/advanced-restkit-development_iphone-sdk/" rel="nofollow">RestKit tutorial</a>. In the middle of the article you will find data about mapping.</p>