Creating a subscriber to get pose of the turtle [closed]

edit

Hi, I just started learning ROS and C++ and I am trying to write a subscriber to get data from /turtle1/pose and print the values. I modified the "listener.cpp" file from the tutorial, but I am confused with how the messages are received through the topic. I had a problem with printing the values form the message in poseCallback function. I got it working, eventually, but only through playing with the code. I don't understand in what form msg is received as well as how the msg->x, msg->y ... syntax works. It's more of a C++ than ROS questions, but I think I have a better chance of finding the answer here. I would also really appreciate any feedback or suggestion on how to make it better/more efficient.

This is full code for the subscriber

#include "ros/ros.h"
#include "turtlesim/Pose.h"

void poseCallback(const turtlesim::Pose::ConstPtr& msg) {

  ROS_INFO("Position of turtle: x:[%f] y:[%f] theta:[%f] linVel:[%f] angVel:[%f]", msg->x, msg->y, msg->theta, msg->linear_velocity, msg->angular_velocity);
}

int main(int argc, char **argv)
{
    ros::init(argc, argv, "getting_pose");
    ros::NodeHandle n;
    ros::Subscriber sub = n.subscribe("/turtle1/pose", 100, poseCallback);
    ros::spin();
    return 0;
}