title: Crash when instantiating ViewController from Storyboard
body: <p>I have got a single view in my storyboard, which I add to my current view by doing the following : </p>
  
  <pre><code>MainViewController *mvc = [self.storyboard instantiateViewControllerWithIdentifier:@"MainController"];
               [self.view addSubview:mvc.view];
  </code></pre>
  
  <p><img src="https://i.stack.imgur.com/t2Rfe.png" alt="storyboard"></p>
  
  <p>The view appears, but everything I do after it appears, leads to a crash. What am I doing wrong ?</p>
  
  <p>Here is an example when it crashes:</p>
  
  <pre><code>-(IBAction)showUsername:(id)sender{
  
      [testLabel setText:@"username"];
  
  }
  </code></pre>
  
  <p>Everything is hooked up in storyboard as well, so falsely linked connections should not cause the problem. </p>