How to add Core Data to existence project on swift

First, Open your APPDelegate.swift and import core data by writing as

import UIKit

import CoreData

Next, add Core data file by click "File" -> "New" -> "File" -> core data on your OS version.

Next, add  NSManagedObjectContext, NSManagedObjectModel and NSPersistentStoreCoordinator to your app delegate to AppDelegate.swift 

You need to change the name of your project name and Data model name.

This is the standard code which is generated when you start your new project.

    

    // MARK: - Core Data stack

    

    lazy var applicationDocumentsDirectory: NSURL = {

       

        let urls = NSFileManager.defaultManager().URLsForDirectory(.DocumentDirectory, inDomains: .UserDomainMask)

        return urls[urls.count-1] as! NSURL

        }()

    

    lazy var managedObjectModel: NSManagedObjectModel = {

   

        let modelURL = NSBundle.mainBundle().URLForResource("DATAMODELNAME", withExtension: "momd")!

        return NSManagedObjectModel(contentsOfURL: modelURL)!

        }()

    

    lazy var persistentStoreCoordinator: NSPersistentStoreCoordinator? = {

    

        var coordinator: NSPersistentStoreCoordinator? = NSPersistentStoreCoordinator(managedObjectModel: self.managedObjectModel)

        let url = self.applicationDocumentsDirectory.URLByAppendingPathComponent("PROJECTNAME.sqlite")

        var error: NSError? = nil

        var failureReason = "There was an error creating or loading the application's saved data."

        if coordinator!.addPersistentStoreWithType(NSSQLiteStoreType, configuration: nil, URL: url, options: nil, error: &error) == nil {

            coordinator = nil

        

            var dict = [String: AnyObject]()

            dict[NSLocalizedDescriptionKey] = "Failed to initialize the application's saved data"

            dict[NSLocalizedFailureReasonErrorKey] = failureReason

            dict[NSUnderlyingErrorKey] = error

            error = NSError(domain: "YOUR_ERROR_DOMAIN", code: 9999, userInfo: dict)

       

            NSLog("Unresolved error \(error), \(error!.userInfo)")

            abort()

        }

        

        return coordinator

        }()

    

    lazy var managedObjectContext: NSManagedObjectContext? = {

   

        let coordinator = self.persistentStoreCoordinator

        if coordinator == nil {

            return nil

        }

        var managedObjectContext = NSManagedObjectContext()

        managedObjectContext.persistentStoreCoordinator = coordinator

        return managedObjectContext

        }()

    

    // MARK: - Core Data Saving support

    

    func saveContext () {

        if let moc = self.managedObjectContext {

            var error: NSError? = nil

            if moc.hasChanges && !moc.save(&error) {

    

                NSLog("Unresolved error \(error), \(error!.userInfo)")

                abort()

            }

        }

    }

Next, add "self.saveContext()" to applicationWillTerminate 

    func applicationWillTerminate(application: UIApplication) {

        // Called when the application is about to terminate. Save data if appropriate. See also applicationDidEnterBackground:.

        self.saveContext()

it's done!


I referred to this website for this work. please check 
http://craig24.com/2014/12/how-to-add-core-data-to-an-existing-swift-project-in-xcode/#comment-34489