Question

I have a class called PublishObject to manage my ros node, however, I only want to publish things when I use ctrl+c to to kill the spin() and return to the main function as following, however I find that when I return to the main function, everything works in the function nodeinstance.secondrunpublishmatched_object(), but I think the publisher is notworking as the rviz doesn't receive anything?

How can I fix this? Or I am supposed only to using Publisher insided the callback function such that it will publish properly??

int main(int argc, char **argv)

  ros::init(argc, argv, "publish_object");
  PublishObject  node_instance;  
  ros::spin();
  node_instance.second_run_publish_matched_object(); // to publish things. 

return 0;
}

Asked by zhonghao on 2018-12-03 07:20:57 UTC

Answer 1

Or I am supposed only to using Publisher insided the callback function such that it will publish properly??

No, you can publish anywhere else as well, except after ros::spin() has returned.

At that point ROS has shut down, so no events (ie: incoming messages or service requests) will be processed, and neither will outgoing messages be transmitted.

Asked by gvdhoorn on 2018-12-03 07:38:20 UTC

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so in this case, how can I return to the main function but still before ros::spin()??Because I need to collect all the msgs from my subsciber first, then I can process it

Asked by zhonghao on 2018-12-03 07:41:49 UTC

you can use ros::spinOnce() in a loop and when you want to exit the loop just break the loop

Asked by Hamid Didari on 2018-12-03 08:57:11 UTC

but in this case when I break the loop, can I still publish things???,I think it shuts down ROS as well.

Asked by zhonghao on 2018-12-03 08:59:42 UTC

for breaking loop you don't need to suht down the node you can use something like this:

while(ros::ok)
{
ros::spinOnce();
if(user_input == 's')
 break;
loop_rate.sleep();
}

Asked by Hamid Didari on 2018-12-03 09:12:32 UTC

ros publisher not publishing

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