How to make a class with publisher and subscriber which is a member of another class

Question

Let's assume I have class cA, which has a node that subscribe from topic and publisher with a "constant" frequency. Class cA is a mamber of class cB. Where I should put "while(ros::ok())" for publishing purpose? Cose if i put it in constructor it'll bloc constructor of "higher" class (ofc. I can make a function cA::Publish() and run everything further in cB::Publish() or split classes to more nodes and classes, but i am looking for beter solution).

Should I use threads? I have never used them so I don't know if i should. I found this cant_post_links_http://wiki.ros.org/roscpp/Overview/Callbacks%20and%20Spinning

Is there an easy example?

thanks in advance

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Originally posted by BP on ROS Answers with karma: 176 on 2014-03-13

Post score: 1

Answer 1

I think the while(ros::ok()) should be somewhere 'global', e. g. in your main function or a single run function. Do not put it to deep into your class hierarchy, it make your code hard to understand.

If you need your class to publish at constant rate and your CPU load is not 'to high' (i. e. not threading needed due to CPU load) I would add a ros::Timer in your class, bind the timer to a class member function and publish in the member function.

Example:

#include <ros/ros.h>
#include <std_msgs/Empty>

#define TIMER_TIMEOUT (0.5F) // in sec

class MyClass
{
  private:

  ros::NodeHandle po_nh;
  ros::Timer po_timer;
  ros::Publisher po_pub;

  void onTimer()
  {
    po_pub.publish( std_msgs::Empty() );
  }

public:
  MyClass( ros::NodeHandle ao_nh ) :
    po_nh( ao_nh )
  {
    po_pub = po_nh.advertise<std_msgs::Empty>( "~empty", 10 ) ;
    po_timer = po_nh.createTimer( ros::Duration( TIMER_TIMEOUT ), boost::bind( &MyClass::onTimer,  this ) );
  }

  virtual ~MyClass()
  {

  }
};

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Originally posted by Wolf with karma: 7555 on 2014-03-13

This answer was ACCEPTED on the original site

Post score: 2