No Matching Member Function for Call to Subscribe

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I am calling subscribe, passing in a class member function and this current instance.

Everything I am doing seems correct to me, but I'm getting No matching member function for call to subscribe. I have annotated the point where the error occurs.

I thought it could be my being rusty with C++ and not initializing my private reference to the nodehandle correctly, but using the parameter to the constructor n has the same effect.

Class declaration:

#pragma once

#include <spencer_tracking_msgs/TrackedPersons.h>
#include <spencer_tracking_msgs/TrackedPerson.h>
#include <geometry_msgs/Point.h>
#include <ros/ros.h>
#include <ros/package.h>
#include <functional>
#include <eigen3/Eigen/Dense>
#include <eigen3/Eigen/Eigenvalues>
#include <deque>
#include <boost/bind.hpp>

/*
  All function and class declarations pertaining to person, object
  tracking goes here.
  All names declared in the namespace must be unique.
*/

using PTCallback = std::function<void(Eigen::Vector2f)>;
const std::string PTRACK_TOPICNAME = "/spencer/perception/tracked_persons";

namespace followlib 
{
  class PeopleTracker
  {
  public:
    /**
    * @brief Create a PeopleTracker with callback for tracked person coordinates
    * @param n: node handle of core app
    * @param cb: callback accepting vector2f points, bound using std::mem_fn()
    ***/
    PeopleTracker(const ros::NodeHandle &n, const PTCallback &cb);

    PeopleTracker (const PeopleTracker&) = delete;
    PeopleTracker& operator= (const PeopleTracker&) = delete;
  private:
    void p_SubCb(const spencer_tracking_msgs::TrackedPersons::ConstPtr &msg);

  private:
    const ros::NodeHandle &p_rosnode;
    const PTCallback &p_cb;
    ros::Subscriber p_ptSub;
  };
}

Class definition:

#include "tracking.h"


namespace followlib
{

PeopleTracker::PeopleTracker(const ros::NodeHandle &n, const PTCallback &cb):
    p_rosnode(n), p_cb(cb) {
  p_ptSub = n.subscribe("spencer/perception/tracked_persons", 
    1000, &PeopleTracker::p_SubCb, this); // error, no matching member function for call to 'subscribe'
}

void PeopleTracker::p_SubCb(const spencer_tracking_msgs::TrackedPersons::ConstPtr &msg)
{ 
  const spencer_tracking_msgs::TrackedPersons &m = *msg;
  if (m.tracks.size() > 0)
  {
    const geometry_msgs::Point &p = m.tracks[0].pose.pose.position;
    Eigen::Vector2f v (p.x, p.y);
    p_cb(v);
  }
}

}

Truncated Compiler Error:

/home/rpg711/kinetic_workspace/sandbox/cs403-semester-project/src/libs/tracking.cpp:9:78: error: no matching function for call to ‘ros::NodeHandle::subscribe(const string&, int, void (followlib::PeopleTracker::*)(const ConstPtr&), followlib::PeopleTracker*) const’
   p_ptSub = n.subscribe(PTRACK_TOPICNAME, 1000, &PeopleTracker::p_SubCb, this);
                                                                              ^
In file included from /opt/ros/kinetic/include/ros/ros.h:45:0,
                 from /home/rpg711/kinetic_workspace/sandbox/cs403-semester-project/include/tracking.h:6

I have also tried using to no success:

 p_ptSub = n.subscribe("spencer/perception/tracked_persons", 
        1000, boost::bind(&PeopleTracker::p_SubCb, this, _1)); // error, no matching member function for call to 'subscribe'

Edit:

I have also tried this to the same error:

  void (PeopleTracker::* fn) (spencer_tracking_msgs::TrackedPersons::ConstPtr)  = &PeopleTracker::p_SubCb;
  p_ptSub = n.subscribe(PTRACK_TOPICNAME, 1, fn, this);

What is going on?