Create a persistent store for Core Data

I did the tutorial on apples site, the Core Data tutorial for iOS and i did this tutorial about 3 times to see if i was mistaken, But when i finish the tutorial, it says that the app should work and be able to add Events to the table view, but when i press the + button, the app crashes and the console says: Cannot do save operation. There is no persistent store

How could i fix this? I checked my code and i have everything!! Thanks in advance!