title: NSLayoutConstraint between Navigation Bar & ViewControllers View
body: <p>Can we add a <code>NSLayoutConstraint</code> between <code>self.navigationcontroller.navigationbar</code> and a view inside the <code>self.view</code>. Here self is a <code>UIViewController</code> instance and <code>_textField</code> is a subview of <code>self.view</code></p>
  
  <p>What I need is that the UI should look alike irrespective whether the <code>navigationBar</code> is Translucent or not.</p>
  
  <p>I've tried the following. But It does not work.</p>
  
  <pre><code>NSLayoutConstraint* cn = [NSLayoutConstraint constraintWithItem:_textField
                                                        attribute:NSLayoutAttributeTop relatedBy:NSLayoutRelationEqual
                                                           toItem:self.navigationController.navigationBar attribute:NSLayoutAttributeBottom
                                                       multiplier:1.0 constant:20];
  [self.navigationcontroller.view addConstraint:cn];
  </code></pre>