title: @Protocol with 2 elements
body: <p>What does </p>
  
  <pre><code>@protocol UIPageViewControllerDelegate, UIPageViewControllerDataSource;
  </code></pre>
  
  <p>mean ? </p>
  
  <p>Does it mean UIPageViewControllerDelegate and UIPageViewControllerDataSource protocols have some methods and properties in common ?</p>