title: How can I call the ViewDidAppear only one time?
body: <p>When the user start the app I want it show the stockholm.xib
  and It does here:</p>
  
  <pre><code>-(void)viewDidAppear:(BOOL)animated{
      [super viewDidAppear:animated];
  
      NSUserDefaults *startPage =[NSUserDefaults standardUserDefaults];
      NSString *page =[startPage stringForKey:@"page"];
      NSLog(page);
  
      if(page==nil)
      {
          //Do nothing
  
      }
      else if ([page isEqualToString:@"Default"])
      {
          //Do nothing
      }
  
      else if ([page isEqualToString:@"Stockholm"])
      {
          NSLog(@"going to Stockholm");
          Stockholm *Start =[[Stockholm alloc]initWithNibName:nil bundle:nil];
          [self presentModalViewController:Start animated:YES];
  
  
      }
      else {
          NSLog(@"HAHA");
  
  }
  </code></pre>
  
  <p>but when user closes the stockholm.xib using:</p>
  
  <pre><code>[self dismissModalViewControllerAnimated:YES];
  </code></pre>
  
  <p>after the animation is done, the app crashes. 
  and the reason is, I guess, viewDidAppear calls twice and therefore it is trying to open the recently closed xib file.</p>
  
  <p>now, how Can I call the view did appear only once? so that when the user comes back from Stockholm the viewDidAppear wont be called? any other solution?</p>
  
  <p>thanx :)</p>