title: this class is not key value coding-compliant for the key view.'
body: <p>I have a problem in AppDelegate, when run the app I get this error:</p>
  
  <pre><code>  Terminating app due to uncaught exception 'NSUnknownKeyException', reason: 
    '[&lt;UIApplication 0x856c820&gt; setValue:forUndefinedKey:]:
     this class is not key value coding-compliant for the key view.'
  </code></pre>
  
  <p>This is the code of AppDelegate.h</p>
  
  <pre><code>#import &lt;UIKit/UIKit.h&gt;
  
  @class ViewController;
  
  @interface AppDelegate : UIResponder &lt;UIApplicationDelegate&gt;{
  
          //UINavigationController *navigationController;
   }
  
  @property (strong, nonatomic) UIWindow *window;
  
  
  @property (copy, nonatomic) ViewController * viewController;
  @property (copy, nonatomic) UINavigationController * navigationController;
  
  
  
   @end
  </code></pre>
  
  <p>This is the code of AppDelegate.m</p>
  
  <pre><code> #import "AppDelegate.h"
  
   #import "RootViewController.h"
  
  
  
    @implementation AppDelegate
  
  
  
    - (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:  (NSDictionary *)launchOptions
     {
          self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];
  
          RootViewController *rootMenu;
  
  
           if ([[UIDevice currentDevice] userInterfaceIdiom] == UIUserInterfaceIdiomPhone) {
                rootMenu= [[RootViewController alloc]  initWithNibName:@"ViewController_iPhone" bundle:nil];
      } else {
                rootMenu = [[RootViewController alloc]initWithNibName:@"ViewController_iPad" bundle:nil];
    }
  
  
    self.navigationController =[[UINavigationController  alloc]initWithRootViewController:rootMenu];
  
    self.window.rootViewController = self.navigationController;
  
    [self.window makeKeyAndVisible];
     return YES;
   }
  </code></pre>
  
  <p>What can I do to resolve this error? I have rewritten the RootViewController, throwing in the trash the old one, but the problem remains the same.Thanks in advance</p>