tf2 tutorial: follower turtle makes circles, doesn't follow leader

edit

OK I found where my problem had stemmed from. The code here is OK as others kindly pointed out in the comments. what was wrong, was the broadcaster that I had written for sending the trutle1/turtle2 transformations.

basically I was instantiating a new broadcaster in my callback and this was the culprit. I had to either make it static or use one instance for this to work(why is that an issue? I still don't know).

So this is my broadcaster I provided some explanation concerning the issue in the comments of callback_fn:

 #include <iostream>
#include <string>
#include <functional>

#include <ros/ros.h>
#include <tf2_ros/transform_broadcaster.h>
#include <geometry_msgs/TransformStamped.h>
#include <turtlesim/Pose.h>
#include <tf/LinearMath/Quaternion.h>

int main(int argc, char** argv)
{
    ros::init(argc, argv, "tf2_broadcaster_node");
    ros::NodeHandle n;
    ros::NodeHandle tmp_node("~");
    std::string turtle_name = "";

    if (!tmp_node.hasParam("turtle"))
    {
        if (argc != 2)
        {
            ROS_ERROR("Number of arguments do not match! must provide a turtle's name as the argument!");
            return -1;
        }
        else
        {
            // Get the second argument which is the turtlename (the first argument is the applications exe path)
            turtle_name = std::string(argv[1]);
            std::cout<<"turtle_name is: "<<turtle_name<<std::endl;
        }
    }
    else
    {
        // if we already have a turtlename in our parameter server, fetch it!
        tmp_node.getParam("turtle", turtle_name);
        std::cout<<"turtle_name: "<<turtle_name<<std::endl;
    }

    // see the comment below, either uncomment this or 
    // the static one below. see the explanation for more details
    //tf2_ros::TransformBroadcaster broadcaster;
    auto callback_fn = [&](turtlesim::PoseConstPtr pose)
    {
        // read https://answers.ros.org/question/381937/
        // short story: it doesn't have to be defined as static or be shared!
        // what matters is that they shouldn't be created/destroyed very fast
        // that is every few milliseconds e.g.
        // or as jvdhoorn says : 
        //  "What is important is to make sure it has a sane lifecycle 
        // (ie: it does not get created and destroyed every few milliseconds)."
        // otherwise, you will end-up with all sorts of nonsensical weird happenings
        // previously I forgot about this and when I ran the listener app which relies 
        // on this, the trutle2 was moving erratically, in circles, it would get close to
        // turtle1, but not always and not as fast, it would take a lot of time and huge
        // circles! remove static and see it yourself.
        // (run tf2_transform_carrot_demo.launch and see the result)
        static tf2_ros::TransformBroadcaster broadcaster;
        geometry_msgs::TransformStamped transform;
        tf::Quaternion qtr;

        // since we want all the nodes to be linked together, here we are specifying
        // one parent called "world" for this node. any other nodes that have this as 
        // parent will be able to communicate with this node. and because our turtles
        // need to be linked in order to  communicate through tf2 this is necessary
        transform.header.frame_id = "world";
        transform.header.stamp = ros::Time::now();
        //this means we are naming our frame after turtlename
        // and our parent frame is world, this allows us to
        // be with other frames that already exist and
        // world is their parent (i.e. this way we can have multiple turtles
        // roaming in the same world ...