How to publish data to ROS from Gazebo plugin

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Hi guys,

I am trying to learn how to publish data over a ROS topic from a Gazebo plugin class. I have attempted to reuse other people's code, but without any luck. I have included the following code that for now, is only attempting to initialise ROS and then publish a String over a custom topic.

class VelodynePlugin : public ModelPlugin
{
    private: ros::NodeHandle* rosnode_;
    private: ros::Publisher pub_;
    private: PubQueue<std_msgs::String>::Ptr pub_Queue;
    private: PubMultiQueue pmq;

    public: virtual void Load(physics::ModelPtr _model, sdf::ElementPtr _sdf)
    {   
        if (!ros::isInitialized()) 
        {
          int argc = 0;
          char **argv = NULL;
          ros::init(argc, argv, "TestSpace", ros::init_options::NoSigintHandler);
        }

        this->rosnode_ = new ros::NodeHandle("TestSpace");
        this->pmq.startServiceThread();
        this->pub_Queue = this->pmq.addPub<std_msgs::String>();
        this->pub_ = this->rosnode_->advertise<std_msgs::String>("/custom", 100);

        std_msgs::String msg;
        msg.data = "hello";
        this->pub_Queue->push(msg, this->pub_);
    }
};

GZ_REGISTER_MODEL_PLUGIN(VelodynePlugin);

When I run this plugin through Gazebo, I can see that the "/custom" topic has been created under "rostopic list", however, when I subscribe to the topic via "rostopic echo /custom", I do not get the "hello" message.

Is anyone able to guide me on what I am missing to properly publish data from the Gazebo plugin so that I can subscribe to it in a ROS program?

Many thanks!