how to bind a callback to include a MessageEvent [closed]

edit

I am trying to use MessageEvent to get topic information in a callback. While I have referred to the example here

and here

I can't figure out how to use boost::bind to tell the subscriber to give me both the PointCloud message and the MessageEvent. Is there an example of this somewhere? Here is what I have, which is definitely wrong:

  sub_cloud_ = nh_.subscribe<sensor_msgs::PointCloud2>
              (input_topic_, 1, 
                boost::bind(&HapticNode::cloudCallback, this, _1, _2));

  void HapticNode::cloudCallback(const sensor_msgs::PointCloud2ConstPtr &input, 
                       const ros::MessageEvent<std_msgs::String const>& event)
  {
    std::string topic;
    const std::string& publisher_name = event.getPublisherName();
    ros::M_string connection_header = event.getConnectionHeader();
    topic = connection_header["topic"];

    ROS_INFO("Got a cloud on topic %s in frame %s with %d points!",
             topic.c_str(), 
             input->header.frame_id.c_str(), 
             input->width*input->height);
  }