title: UITableViewDataSource Delegate
body: <p>I created a new Master-Detail Application from Xcode template</p>
  
  <p>I found that the main interface ( in this case BirdMasterViewController ) inherit from UITableViewController,
  and UITableViewController conform to UITableViewDataSource protocol</p>
  
  <p>so I can specify methods like</p>
  
  <pre><code>- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView
  {
      return 1;
  }
  </code></pre>
  
  <p>But I did not find a set delegate to _dataSource variable on BirdMasterViewController, like</p>
  
  <pre><code>xxxxxx._dataSource = self; or setDataSource: self
  </code></pre>
  
  <p>to set _dataSource object</p>
  
  <pre><code>// to this
  id &lt;UITableViewDataSource&gt;  _dataSource;
  </code></pre>
  
  <p>Why the delegation can run ?</p>