title: How to add Core Data to an already created iOS project
body: <p>I forgot to check Use Core Data for my project.
  How can I include Core Data using Swift?</p>
  
  <p>I already added Data Model, CoreData.fraMework, </p>
  
  <p>I got the error message : Use of unresolved identifier 'managedObjectContext'</p>
  
  <pre><code>    let destination = NSEntityDescription.insertNewObjectForEntityForName(
          entityName,
          inManagedObjectContext: managedObjectContext!) as Destination
  </code></pre>