How do i use the variables from the joyCallback function in the OpenCVCallback?

edit

I'm not too familiar with programming and C++ so i apologise in advance for any misinformation. Using the turtlesim Teleoperation Node with joystick from http://wiki.ros.org/joy/Tutorials/Wri... , I intend to change the movements of the turtlesim based on the value of msg->data from the OpenCVCallback function. The msg->data is a integer value.

The intended outcome is such that when msg->data is more than 200, the turtlesim will not be able to move using the joystick control.

Is there a way where i can make use of the variables like twist.angular.z from the joyCallback function inside the OpenCVCallback function? The code will be something like this :

void TeleopTurtle::OpenCVCallback(const std_msgs::Int16::ConstPtr& msg)
{


  ROS_INFO("I heard [%d]", msg->data );
  if( (msg->data) >=200 )
{   

    twist.angular.z = 0;
    twist.linear.x = 0;
//the turtlesim will not be able to move using the joystick

}

Code

#nclude <ros/ros.h>
#include <geometry_msgs/Twist.h>
#include <sensor_msgs/Joy.h>
#include <std_msgs/Int16.h>


int a;
class TeleopTurtle
{
public:
  TeleopTurtle();

private:
  void joyCallback(const sensor_msgs::Joy::ConstPtr& joy);
  void OpenCVCallback(const std_msgs::Int16::ConstPtr& msg);

  ros::NodeHandle nh_;

  int linear_, angular_;
  double l_scale_, a_scale_;
  ros::Publisher vel_pub_;
  ros::Subscriber joy_sub_;
  ros::Subscriber opencv_sub_;
  ros::Subscriber twist_sub_;


};


TeleopTurtle::TeleopTurtle():   
  linear_(1),
  angular_(2)
{

  nh_.param("axis_linear", linear_, linear_);
  nh_.param("axis_angular", angular_, angular_);
  nh_.param("scale_angular", a_scale_, a_scale_);
  nh_.param("scale_linear", l_scale_, l_scale_);


  vel_pub_ = nh_.advertise<geometry_msgs::Twist>("turtle1/cmd_vel", 1);


  joy_sub_ = nh_.subscribe<sensor_msgs::Joy>("joy", 10, &TeleopTurtle::joyCallback, this);

  opencv_sub_ = nh_.subscribe<std_msgs::Int16>("chatter", 10, &TeleopTurtle::OpenCVCallback, this);





}

void TeleopTurtle::joyCallback(const sensor_msgs::Joy::ConstPtr& joy)
{  
  geometry_msgs::Twist twist;
  twist.angular.z = a_scale_*joy->axes[angular_];
  twist.linear.x = l_scale_*joy->axes[linear_];
  a = twist.angular.z ;
  vel_pub_.publish(twist);
}

void TeleopTurtle::OpenCVCallback(const std_msgs::Int16::ConstPtr& msg)
{


  ROS_INFO("I heard [%d]", msg->data );
  if( (msg->data) >=200 )
{   

//the turtlesim will not be able to move using the joystick

}

}


int main(int argc, char** argv)
{
  ros::init(argc, argv, "teleop_turtle");
  TeleopTurtle teleop_turtle;



  ros::spin();
}

Here's what i tried:

#include <ros/ros.h>
#include <geometry_msgs/Twist.h>
#include <sensor_msgs/Joy.h>
#include <std_msgs/Int16.h>



class TeleopTurtle
{
public:
  TeleopTurtle();

private:
  void joyCallback(const sensor_msgs::Joy::ConstPtr& joy);
  void OpenCVCallback(const std_msgs::Int16::ConstPtr& msg);

  ros::NodeHandle nh_;

  int linear_, angular_;
  double l_scale_, a_scale_;
  ros::Publisher vel_pub_;
  ros::Subscriber joy_sub_;
  ros::Subscriber opencv_sub_;
  ros::Subscriber twist_sub_;


};


TeleopTurtle::TeleopTurtle():   
  linear_(1),
  angular_(2)
{

  nh_.param("axis_linear", linear_, linear_);
  nh_.param("axis_angular", angular_, angular_);
  nh_.param("scale_angular", a_scale_, a_scale_);
  nh_.param("scale_linear", l_scale_, l_scale_);


  vel_pub_ = nh_.advertise<geometry_msgs::Twist>("turtle1/cmd_vel", 1);


  joy_sub_ = nh_.subscribe<sensor_msgs::Joy>("joy", 10, &TeleopTurtle::joyCallback, this);

  opencv_sub_ = nh_.subscribe<std_msgs::Int16>("chatter", 10, &TeleopTurtle::OpenCVCallback, this);





}

void TeleopTurtle::joyCallback(const sensor_msgs::Joy::ConstPtr& joy)
{  
  geometry_msgs::Twist twist;
  TeleopTurtle::twist.angular.z = a_scale_*joy->axes[angular_];
  TeleopTurtle::twist.linear.x = l_scale_*joy->axes[linear_];
  vel_pub_.publish(twist);
}

void TeleopTurtle::OpenCVCallback(const std_msgs::Int16::ConstPtr& msg)
{


  ROS_INFO("I heard [%d]", msg->data ...