title: how to refresh the viewdidload for parent viewcontroller
body: <p>I have 2 viewcontrollers with segue "page curl"</p>
  
  <p>viewcontrollerA => pagecurl => viewcontrollerB
  and Now I want to update viewcontrollerA since user make some change at viewcontrollerB.</p>
  
  <p>I tryed:</p>
  
  <pre><code>UIStoryboard*  sb = [UIStoryboard storyboardWithName:@"mystoryboard"
                                            bundle:nil];
  UIViewController* vc = [sb instantiateViewControllerWithIdentifier:@"ExampleViewController"];
  [vc ViewDidLoad]; // or ViewWillAppear or ViewDidApear
  </code></pre>
  
  <p>it works only for the NSLog I put in those functions. 
  but none of them works with the function which check out Coredata and update the interface.
  please help</p>