title: duplicate interface declaration for class 'test_coredataAppDelegate'
body: <p>two errors suddenly fired in this piece of code 
  - duplicate interface declaration for class 'test_coredataAppDelegate' 
  - redefinition of 'struct test_coredataAppDelegate'</p>
  
  <pre><code>#import &lt;UIKit/UIKit.h&gt;
  #import &lt;CoreData/CoreData.h&gt;
  
  @interface test_coredataAppDelegate : NSObject &lt;UIApplicationDelegate, UITabBarControllerDelegate&gt; {
  
      ///////////////////New parts /////////////////////////
      NSManagedObjectModel *managedObjectModel;
      NSManagedObjectContext *managedObjectContext;       
      NSPersistentStoreCoordinator *persistentStoreCoordinator;
  
      //////////////////////////////////////////////
      UIWindow *window;
      UITabBarController *tabBarController;
  }
  @property (nonatomic, retain, readonly) NSManagedObjectModel *managedObjectModel;
  @property (nonatomic, retain, readonly) NSManagedObjectContext *managedObjectContext;
  @property (nonatomic, retain, readonly) NSPersistentStoreCoordinator *persistentStoreCoordinator;
  
  @property (nonatomic, retain) IBOutlet UIWindow *window;
  @property (nonatomic, retain) IBOutlet UITabBarController *tabBarController;
  
  @end
  </code></pre>
  
  <p>how to fix that please </p>
  
  <p>Best regards </p>