title: How to Update addTarget method to swift 4
body: <p>when update project code to swift 4 get some error for add.target method
  how i can fix this error?</p>
  
  <pre><code> //swift3
  
  var chatLogController: ChatLogController? {
      didSet {
          sendButton.addTarget(chatLogController, action: #selector(ChatLogController.handleSend), for: .touchUpInside)
  
         uploadImageView.addGestureRecognizer(UITapGestureRecognizer(target: chatLogController, action: #selector(ChatLogController.handleUploadTap)))
      }
  }
  </code></pre>