title: present a controller with alpha is 0.5
body: <p>The new UIViewController named <em>vc</em> for example, then call</p>
  
  <p><code>[self presentViewController:vc animated:YES completion:nil];</code></p>
  
  <p>I want  <em>vc</em> looks like transparent or alpha = 0.5,</p>
  
  <p>I know the code below can do that, bu the present animation disappear, I want both <strong>transparent</strong> and <strong>annimation</strong>, any idear?</p>
  
  <p><code>self.modalPresentationStyle = UIModalPresentationCurrentContext;</code></p>