Synchronizer with approximate time policy in a class [C++]

edit

I have been trying to implement a synchronizer with approximate time policy in a class. The following code compiles with no problem. But how should I define the Synchronizer and the registerCallback? (The two commented lines)

#include "header.h"
using namespace message_filters;
typedef control_sys::IntWithHeader myMsg;

class Node
{

public:

    Node()
{
    sub1.subscribe(node, "in1", 1);
    sub2.subscribe(node, "in2", 1);

}
    void callback(const myMsg &in1, const myMsg &in2)
{
        std::cout << "Synchronization successful" << std::endl;
}   


private:

    ros::NodeHandle node;
    ros::Publisher pub;
    std_msgs::Int32 out;
    message_filters::Subscriber<myMsg> sub1;
    message_filters::Subscriber<myMsg> sub2;
    typedef sync_policies::ApproximateTime<myMsg, myMsg> MySyncPolicy;
    // This is how I would define them inside main()
    //Synchronizer<MySyncPolicy> sync(MySyncPolicy(10), sub1, sub2);
    //sync.registerCallback(&callback);
};

int main(int argc, char **argv)
{

    ros::init(argc, argv, "synchronizer");
    Node synchronizer;

    ros::spin();

}

Update 1: Headers included:

#include <ros/ros.h>
#include <std_msgs/Int32.h>
#include <iostream>
#include <message_filters/subscriber.h>
#include <message_filters/synchronizer.h>
#include <message_filters/sync_policies/approximate_time.h>
#include "control_sys/IntWithHeader.h"

Update 2: Error output of catkin_make (in terminal)