Cpp error: expected initializer before ‘:’ token

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Hello, I am using Ubuntu 14.04 and ROS Indigo with Gazebo 2.2.6. I am trying to compile a gazebo ros plugin. Here is the code.

armbot_plugin.hpp:

 #ifndef _ARMBOT_PLUGIN_HH_
 #define _ARMBOT_PLUGIN_HH_

 #include <iostream>
 #include <ros/ros.h>
 #include <geometry_msgs/Twist.h>
 #include <gazebo/common/Plugin.hh>

 namespace gazebo{

 class GAZEBO_VISIBLE RobotDriver : public WorldPlugin
 {
 private:
   //! The node handle we'll be using
   ros::NodeHandle nh_;
  //! We will be publishing to the "/base_controller/command" topic to issue commands
  ros::Publisher cmd_vel_pub_;

   public:
     //! ROS node initialization
     RobotDriver(ros::NodeHandle &nh) : WorldPlugin()
  {
    nh_ = nh;
    //set up the publisher for the cmd_vel topic
    cmd_vel_pub_ = nh_.advertise<geometry_msgs::Twist>("/base_controller/command", 1);
  }

  //! Loop forever while sending drive commands based on keyboard input
  bool driveKeyboard()
  {
    std::cout << "Type the angle in rads (0,0.5) and press enter  "
      "Press '.' to exit.\n";

    //we will be sending commands of type "twist"
    geometry_msgs::Twist base_cmd;

 int cmd;
 while(nh_.ok()){

 std::cin >> cmd;
 if(cmd>0.5 || cmd<0  && cmd!='.')
 {
   std::cout << "unknown command:" << cmd << "\n";
   continue;
   }

   //base_cmd.linear.x = base_cmd.linear.y = base_cmd.angular.z = 0;
   //turn left (yaw) and drive forward at the same time

   //quit
  else if(cmd=='.'){
     break;
   }
   else {
     base_cmd.angular.y = cmd;
   }

 std::cout << "Type the twist in rads (-0.5,0.5) and press enter  "
   "Press '.' to exit.\n";
   cmd=0;
   std::cin >> cmd;
   if(cmd>0.5 || cmd<-0.5  && cmd!='.')
   {
     std::cout << "unknown command:" << cmd << "\n";
     continue;
   }

   //quit
  else if(cmd=='.'){
     break;
   }
 else {
     base_cmd.angular.z = cmd;
   }
   //publish the assembled command
   cmd_vel_pub_.publish(base_cmd);
 }
 return true;
  }
   };
   }
   #endif

armbot_plugin.cpp:

 #include <iostream>
 #include <ros/ros.h>
 #include <geometry_msgs/Twist.h>
 #include "armbot_plugin.hpp"

 using namespace gazebo;
 GZ_REGISTER_WORLD_PLUGIN(RobotDriver)

 int main(int argc, char** argv)
 {
   //init the ROS node
   ros::init(argc, argv, "robot_driver");
   ros::NodeHandle nh;

   RobotDriver driver(nh);
   driver.driveKeyboard();
   }

and I get the following errors

 In file included from /home/sofia/catkin_ws/src/armbot_plugin/src/armbot_plugin.cpp:4:0:
 /home/sofia/catkin_ws/src/armbot_plugin/src/armbot_plugin.hpp:13:34: error: expected initializer before ‘:’ token
  class GAZEBO_VISIBLE RobotDriver : public WorldPlugin
                                   ^
 /home/sofia/catkin_ws/src/armbot_plugin/src/armbot_plugin.cpp:18:1: error: expected ‘}’ at end of input
  }
  ^
 make[2]: *** [armbot_plugin/CMakeFiles/armbot_plugin.dir/src/armbot_plugin.cpp.o] Error 1
 make[1]: *** [armbot_plugin/CMakeFiles/armbot_plugin.dir/all] Error 2
 make: *** [all] Error 2

If I remove the "GAZEBO_VISIBLE" Macro I get this error:

 In file included from /home/sofia/catkin_ws/src/armbot_plugin/src/armbot_plugin.hpp:8:0, from           /home/sofia/catkin_ws/src/armbot_plugin/src/armbot_plugin.cpp:4:      /home/sofia/catkin_ws/src/armbot_plugin/src/armbot_plugin.cpp: In function ‘gazebo::WorldPlugin* RegisterPlugin()’:      /usr/include/gazebo-2.2/gazebo/common/Plugin.hh:408:26: error: cannot allocate an object of abstract type      ‘gazebo::RobotDriver’ return new classname();\ ^ /home/sofia/catkin_ws/src/armbot_plugin/src/armbot_plugin.cpp:8:1: note:      in expansion of macro ‘GZ_REGISTER_WORLD_PLUGIN’ GZ_REGISTER_WORLD_PLUGIN(RobotDriver) ^ In file included      from /home/sofia/catkin_ws/src/armbot_plugin/src/armbot_plugin.cpp:4:0:      /home/sofia/catkin_ws/src/armbot_plugin/src/armbot_plugin.hpp:13:7: note: because the following virtual ...