Ros service not advertised in functions

edit

Followed the tutorial, adapted it to my project. When I call the advertiseService in the main, it works. When it is called in a function called by main, it doesn't.

Here some code. First, tutorial example which works :

#include "ros/ros.h"
#include "testService/AddTwoInts.h"

bool add(testService::AddTwoInts::Request  &req, testService::AddTwoInts::Response &res)
{
  res.sum = req.a + req.b;
  ROS_INFO("request: x=%ld, y=%ld", (long int)req.a, (long int)req.b);
  ROS_INFO("sending back response: [%ld]", (long int)res.sum);
  return true;
}

int main(int argc, char **argv)
{
  ros::init(argc, argv, "add_two_ints_server");
  ros::NodeHandle n;

  ros::ServiceServer service = n.advertiseService("add_two_ints", add);
  ROS_INFO("Ready to add two ints.");
  ros::spin();

  return 0;
}

In my use case, I need to set up a service in a separate file. I"m surprised this doesn't work

#include "ros/ros.h"
#include "testService/AddTwoInts.h"

void testFunction(ros::NodeHandle &n);

bool add(testService::AddTwoInts::Request  &req,
         testService::AddTwoInts::Response &res)
{
  res.sum = req.a + req.b;
  ROS_INFO("request: x=%ld, y=%ld", (long int)req.a, (long int)req.b);
  ROS_INFO("sending back response: [%ld]", (long int)res.sum);
  return true;
}

int main(int argc, char **argv)
{
  ros::init(argc, argv, "add_two_ints_server");
  ros::NodeHandle n;

  testFunction(n);

  ROS_INFO("Ready to add two ints.");
  ros::spin();

  return 0;
}

void testFunction(ros::NodeHandle &n)
{
  ros::ServiceServer service = n.advertiseService("add_two_ints", add);  
}

The service doesn't show up when typing rosservice list.

First, I made a new node handle in my function. Then, I tried to pass the main's node Handle by value, reference, pointer, global variable to my function. No changes. I thought about creating a function returning an object with topic name and function pointer inside it, but function pointer callback are callback-specific and my main can't know their type. Any one got a lead to how to do this?