Core Data issue - Swift 2.0

It's the first time i'm implementing the Core Data framework. The logic i'm following is the following - i've created the Data Model (called Db with three Attributes - "Line", "Opt1", "Opt2" all are strings).

Then i've implemented the following code inside a function that runs on viewDidLoad

func startme(){

// i'm appending the NSManagedObject arrays

    let managedContext = appDelegate.managedObjectContext!
    let entity = NSEntityDescription.entityForName("Db", inManagedObjectContext: managedContext)
    let opt1 = NSManagedObject(entity: entity!, insertIntoManagedObjectContext: managedContext)
    let opt2 = NSManagedObject(entity: entity!, insertIntoManagedObjectContext: managedContext)
    let question = NSManagedObject(entity: entity!, insertIntoManagedObjectContext: managedContext)

    opt1.setValue(myoptarray["start"]![0], forKey:"Opt1")
    opt2.setValue(myoptarray["start"]![1], forKey:"Opt2")
    question.setValue(linesmain["start"]!, forKey:"line")

    myDataAnswersArray1.append(opt1)
    myDataAnswersArray2.append(opt2)
    myDataArray.append([question]) // this is an array of arrays

 // implementing the required try catch

    do {
        try managedContext.save()
    }
    catch {
        print("Could not save \(error)") }

 // now after appending the arrays i'm inserting the data into the tableview

    self.tableView1.beginUpdates()
    let insertedIndexPathRange = 0..<linesmain["start"]!.count + 1
    insertedIndexPaths = insertedIndexPathRange.map { NSIndexPath(forRow: $0, inSection: 0) }
    self.tableView1.insertSections(NSIndexSet(index: self.myDataArray.count - 1), withRowAnimation: .Fade)
    self.tableView1.insertRowsAtIndexPaths(insertedIndexPaths, withRowAnimation: .Fade)
    self.tableView1.endUpdates()
}

yet after compiling the build i get those runtime errors:

2015-09-10 17:59:19.684 MyApp[18958:1295418] CoreData:
error: -addPersistentStoreWithType:SQLite configuration:(null)
URL:file:///Users/mihailseglov/Library/Developer/CoreSimulator/Devices/99956E87-379A-4BCF-953E-5EBC96527728/data/Containers/Data/Application/A97E585E-9692-4792-8C9C-144C1887784A/Documents/MyApp.sqlite
options:(null) ... returned error Error Domain=NSCocoaErrorDomain
Code=134100 "(null)" UserInfo={metadata={
NSPersistenceFrameworkVersion = 637;
NSStoreModelVersionHashes = {
Db = <7cdf7bfe 26a5b3cf 2e7f1c77 bd6cdfd1 2c51953e 77890483 b76cc39f 4c7dfb38>;
}; NSStoreModelVersionHashesVersion = 3;
NSStoreModelVersionIdentifiers = (
""
);
NSStoreType = SQLite;
NSStoreUUID = "758FA531-A288-4A60-B70B-24168CDE21B8";
"_NSAutoVacuumLevel" = 2; }, reason=The model used to open the store is
incompatible with the one used to create the store} with userInfo dictionary

I'm not sure what it means and how to overcome it. Any ideas are very welcome!