title: IOS button pressed event?
body: <p>I'm would like to know what it is the difference between:</p>
  
  <pre><code>- (IBAction)operationPressed:(UIButton *)sender {
  
  }
  </code></pre>
  
  <p>and: </p>
  
  <pre><code>- (IBAction)operationPressed:(id)sender {
  
  
  }
  </code></pre>
  
  <p>I can see the xcode try to put more extra help with the auto complete when using the id.
  so which one is the <strong><em>correct</em></strong> to use and why?</p>
  
  <p>thanks</p>