title: How to put a badge on customized UIBarButtonItem
body: <p>I have a navigation bar with two buttons, one is a back button the other a chat symbol.</p>
  
  <p>I write this code like this:</p>
  
  <pre><code>UIBarButtonItem *_btn=[[UIBarButtonItem alloc]initWithImage:[UIImage imageNamed:@"back.png"]
                                                        style:UIBarButtonItemStylePlain
                                                       target:self
                                                       action:@selector(goBackToPreviousView)];
  
  self.navigationItem.leftBarButtonItem=_btn;
  self.navigationItem.leftBarButtonItem.tintColor = [UIColor blackColor];
  
  
  UIBarButtonItem *_btn2=[[UIBarButtonItem alloc]initWithImage:[UIImage imageNamed:@"chat.png"]
                                                        style:UIBarButtonItemStylePlain
                                                       target:self
                                                       action:@selector(startChat)];
  
  self.navigationItem.rightBarButtonItem=_btn2;
  self.navigationItem.rightBarButtonItem.tintColor = [Utility colorWithHexValue:CyanBlue];
  </code></pre>
  
  <p>The problem I have is that whenever there is some new messages in the chat that I have not seen, there should be like a badge of some sort, or a customized label over the chat button, to indicate how many new messages you have.</p>
  
  <p>How do I do this?</p>