title: Calling Objective - C delegate method in swift
body: <p>I have a method declared in Objective-C protocol:</p>
  
  <pre><code>@protocol QMChatConnectionDelegate &lt;NSObject&gt;
  @optional
  - (void)chatServiceChatDidConnect:(QMChatService *)chatService;
  </code></pre>
  
  <p>I want to use this method as callback in my .swift file. My question what is difference between using <code>chatServiceChatDidConnect</code> method directly in class body or adding it as part of extension:</p>
  
  <pre><code>class Chat: NSObject, QMChatConnectionDelegate
  {
  ...
    func chatServiceChatDidConnect(chatService: QMChatService!) {
      print("connected")
    }
  }
  </code></pre>
  
  <p>or </p>
  
  <pre><code>class Chat: NSObject, QMChatConnectionDelegate
  {
  ...
  }
  
  extension Chat: QMChatConnectionDelegate {
      func chatServiceChatDidConnect(chatService: QMChatService!) {
          print("connected")
      }
  }
  </code></pre>
  
  <p>and do I need to declare it as <code>extension Chat : QMChatConnectionDelegate {}</code> or just <code>extension Chat {}</code></p>