A demo of Core Data's Fetch, Insert , Update

keep_user_info_into_local_storage.swift

    private func keep_user_info_into_local_storage(json: JSON){
        // If success, store the returned credential into Core.Data
        
        // 1. Try to retrieve existing record
        let managed_object_context = app_delegate.managed_object_context
        
        // 2. Fetch AuthenticatedUser record
        let fetch_request = NSFetchRequest(entityName: "AuthenticatedUser")
        
        // 3. Execute fetch request
        do{
            let results = try managed_object_context.executeFetchRequest(fetch_request)
            var authenticated_users = results as! [NSManagedObject]
            var authenticated_user :NSManagedObject?
            if (authenticated_users.count > 0){
                // Update existing
                authenticated_user = authenticated_users[authenticated_users.count - 1]
            }
            else {
                // Create & add a new one
                let entity_description =
                    NSEntityDescription.entityForName("AuthenticatedUser", inManagedObjectContext: managed_object_context)
                
                authenticated_user =
                    NSManagedObject(entity: entity_description!, insertIntoManagedObjectContext: managed_object_context)
            }
            
            authenticated_user!.setValue(true, forKeyPath: "is_authenticated")
            authenticated_user!.setValue(json["userId"].stringValue, forKeyPath: "user_id")
            authenticated_user!.setValue(json["id"].stringValue, forKeyPath: "token")
            authenticated_user!.setValue(json["ttl"].stringValue, forKeyPath: "ttl")
            if let fullname :String? = json["first_name"].stringValue + json["last_name"].stringValue {
                authenticated_user!.setValue(fullname, forKeyPath: "full_name")
            }
            
            // TODO: Load addiitonal authenticated user's info (profile picture, first_name, last_name)from somewhere
//            authenticated_user!.setValue(json["email"].stringValue, forKeyPath: "email")
//            authenticated_user!.setValue(json["username"].stringValue, forKeyPath: "user_name")
//            authenticated_user!.setValue(json["first_name"].stringValue, forKeyPath: "first_name")
            
            app_delegate.save_context(nil)
        }
        catch let error as NSError {
            print("Could not fetch record: \(error)")
        }
    }