Adding Core Data to existing iPhone project

All the CoreData header files are imported in App_Prefix.pch, so the CoreData classes will be available throughout your Project, so you don't have to manually import the header in the files you need them.

So open up Xcode and look for some file like App_Prefix.pch, by default it's in the Other Sources group. After the UIKit import statement, add the following line:

#import <CoreData/CoreData.h>

And you should be ready to go.

Xcode 4

For projects created in Xcode 4, the prefix file can be found in the Supporting Files group in the Project navigator. It's called 'projectname-Prefix.pch' by default.

Xcode 6+

Starting with Xcode 6, the precompiled header file is no longer included by default. This is because of the introduction of Modules, which take away the need to use precompiled headers. While it is still possible to manually add a PCH file to globally include the CoreData headers, consider specifying the CoreData dependency using @import CoreData;* in every file that uses CoreData. This makes dependencies explicit and more importantly will avoid this question's problem in the future.

_{* Modules need to be enabled for this to work.}

Try creating Core Data backed Cocoa application and look at AppDelegate. You'll see core data stack implementation methods there as well as managed object model file for defining your entities and other core-data releated stuff.

You've shown us only header (i.e. declaration), but not implementation (i.e. definition) of the Core Data stack.

As Eimantas stated your missing the implementiation of the Core Stack, like

- (NSManagedObjectContext *) managedObjectContext;
- (NSManagedObjectModel *)managedObjectMode;
- (NSPersistentStoreCoordinator *)persistentStoreCoordinator;

On solution would be to create a new core data driver project and copy / paste the implementation to your project.

//in Swift 2.2 , you may do the following without changing the AppDelegate file.

1. Project->targets-->linked frameworks and libraries Now add a new framework (click on +) 'CoreData'
2. File->new file->CoreData->DataModel name it as say A.xcdatamodelid
3. In A.xcdatamodelid create new enitity (click on entity+) name it as say Bc and set its class as 'Bc' in inspector window on right.
4. Now Add attributes to the entity (click on attributes +) , add one attribute for eg : name and its type as String.
5. Now editor->create NSManagedObject Subclass -->click next on the pop up window-->again next-->then click create. Two new files will be created 1. a new class named Bc.swift and an extension named Bc+coredataproperties.swift.

6. File->new file->ios->cocoa Touch class-->set its subclass as NSObject->name it as DataController.swift Inside the file include ///

   import UIKit import CoreData class DataController: NSObject {

   var managedObjectContext: NSManagedObjectContext
   
   override  init() {
       // This resource is the same name as your xcdatamodeld contained in your project.
       guard let modelURL = NSBundle.mainBundle().URLForResource("A", withExtension:"momd") else {
           fatalError("Error loading model from bundle")
       }
       // The managed object model for the application. It is a fatal error for the application not to be able to find and load its model.
       guard let mom = NSManagedObjectModel(contentsOfURL: modelURL) else {
           fatalError("Error initializing mom from: \(modelURL)")
       }
       let psc = NSPersistentStoreCoordinator(managedObjectModel: mom)
       self.managedObjectContext = NSManagedObjectContext(concurrencyType: .MainQueueConcurrencyType)
       self.managedObjectContext.persistentStoreCoordinator = psc
   
       let urls = NSFileManager.defaultManager().URLsForDirectory(.DocumentDirectory, inDomains: .UserDomainMask)
       let docURL = urls[urls.endIndex-1]
       /* The directory the application uses to store the Core Data store file.
       This code uses a file named "A.sqlite" in the application's documents directory.
       */
       let storeURL = docURL.URLByAppendingPathComponent("A.sqlite")
       do {
           try psc.addPersistentStoreWithType(NSSQLiteStoreType, configuration: nil, URL: storeURL, options: nil)
       } catch {
           fatalError("Error migrating store: \(error)")
       }
   
   }
   

   }

//////

7. Now inside the viewcontroller file you can access your db using two methods. Important : include the statement in your viewController "import CoreData" a. call seed() -->to insert value into db/entity b. call fetch()--> to fetch value from db/entity

///////seed()-->def

func seedPerson() {

        // create an instance of our managedObjectContext
        let moc = DataController().managedObjectContext

        // we set up our entity by selecting the entity and context that we're targeting
        let entity = NSEntityDescription.insertNewObjectForEntityForName("Bc", inManagedObjectContext: moc) as! Bc

        // add our data
        entity.setValue("Meera", forKey: "name")


        // we save our entity
        do {
            try moc.save()
        } catch {
            fatalError("Failure to save context: \(error)")
        }
    }

//fetch() def

func fetch() {
        let moc = DataController().managedObjectContext
        let personFetch = NSFetchRequest(entityName: "Bc")

        do {
            let fetchedPerson = try moc.executeFetchRequest(personFetch) as! [Bc]
            print(fetchedPerson.first!.name!)

        } catch {
            fatalError("Failed to fetch person: \(error)")
        }
    }

 let alert  = UIAlertController(title:"Error", message: "No Internet Connection", preferredStyle: .alert)
            alert.addAction(UIAlertAction(title: "Ok", style: .default, handler: { (action) in}))
            alert.addAction(UIAlertAction(title: "Try Again", style: .default, handler: { (action) in
                self.networkCall(text: self.daySelected)
            }))
            self.present(alert, animated: false, completion: nil)