Mantle
Model framework for Cocoa and Cocoa Touch
...Nonetheless, if you're using or want to use Core Data in your app already, Mantle can still be a convenient translation layer between the API and your managed model objects. In order to serialize your model objects from or into JSON, you need to implement <MTLJSONSerializing> in your MTLModel subclass. Mantle doesn't automatically persist your objects for you. However, MTLModel does conform to <NSCoding>, so model objects can be archived to disk using NSKeyedArchiver.