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Gazebo plugin: unable to use world ptr in service

I am trying to make a plugin which creates a service that can run Gazebo for a specific number of physics loops.

So, I made this:

#include <rl_gazebo/run_physics.h>

#include <std_msgs/String.h>

namespace gazebo {

GazeboRunPhysicsPlugin::GazeboRunPhysicsPlugin() { }

GazeboRunPhysicsPlugin::~GazeboRunPhysicsPlugin() {
  delete node_handle_;

void GazeboRunPhysicsPlugin::Load(physics::WorldPtr _world, sdf::ElementPtr _sdf) {
  // Make sure the ROS node for Gazebo has already been initialized
  if (!ros::isInitialized()) {
    ROS_FATAL_STREAM("A ROS node for Gazebo has not been initialized, unable to load plugin. "
      << "Load the Gazebo system plugin '' in the gazebo_ros package)");

  world_ = _world;
  node_handle_ = new ros::NodeHandle;
  service_ = node_handle_->advertiseService("run_physics_loops", &GazeboRunPhysicsPlugin::RunPhysicsLoops, this);

bool RunPhysicsLoops(rl_msgs::RunPhysicsLoops::Request &req,
                     rl_msgs::RunPhysicsLoops::Response &res) {
  int nloops = req.num_loops;
  world_->RunBlocking(nloops); // ERROR Here
  return true;

// Register this plugin with the simulator

} // namespace gazebo

I get a compilation error at the point world_->RunBlocking(nloops); which says:

.../src/ In function ‘bool gazebo::RunPhysicsLoops(rl_msgs::RunPhysicsLoops::Request&, rl_msgs::RunPhysicsLoops::Response&)’:
.../src/ error: ‘world_’ was not declared in this scope

What i am trying to do ...

I have a ros node which has it's own main loop - and in each oop of that I want to run gazebo's physics loop 10 (for example) times. I was using the ros services/topics to communicate with gazebo because I am using hector_quadrotor - which requires gazebo to be run using gazebo_ros.

Hence, I cannot make a gazebo server inside my rosnode - and need it to be run separately. So, I need a ros-service which should be able to call the line world->runBlocking(10). After a little digging I found a plugin can do this and now am trying to make one.