The site is read-only. Please transition to use Robotics Stack Exchange
| ROS Resources: Documentation | Support | Discussion Forum | Index | Service Status | ros @ Robotics Stack Exchange |
 | 1 | initial version |
Does that mean, that a subscriber in ROS HAS to CONTINUOUSLY listen to the topic being published? What if I don't want to? What if I want to listen to a topic say, only when 'flag' is set to 1?
In short: no, you don't have to, you can (re)subscribe and unsubscribe at any time. Subscription you know (NodeHandle::subscribe(..)), to stop a subscription, use NodeHandle::shutdown(). Now subscribe on flag == 1, then shutdown on flag == 0. Keep in mind that it can take some time for your subscription to be processed (as was already mentioned by @Lorenz in your other question).
| | 2 | No.2 Revision |
Does that mean, that a subscriber in ROS HAS to CONTINUOUSLY listen to the topic being published? What if I don't want to? What if I want to listen to a topic say, only when 'flag' is set to 1?
In short: no, you don't have to, you can (re)subscribe and unsubscribe at any time. Subscription you know (NodeHandle::subscribe(..)), to stop a subscription, use NodeHandle::shutdown(). Now subscribe on flag == 1, then shutdown on flag == 0. Keep in mind that it can take some time for your subscription to be processed (as was already mentioned by @Lorenz in your other question).
Instead of (re|un)subscribing, you could also check for flag == 1 in your callback, and only write to your file if the condition is true.
| | 3 | No.3 Revision |
Does that mean, that a subscriber in ROS HAS to CONTINUOUSLY listen to the topic being published? What if I don't want to? What if I want to listen to a topic say, only when 'flag' is set to 1?
In short: no, you don't have to, you can (re)subscribe and unsubscribe at any time. Subscription you know (NodeHandle::subscribe(..)), to stop a subscription, use NodeHandleNodeHandle::shutdown()Subscriber::shutdown()flag == 1, then shutdown on flag == 0. Keep in mind that it can take some time for your subscription to be processed (as was already mentioned by @Lorenz in your other question).
Instead of (re|un)subscribing, you could also check for flag == 1 in your callback, and only write to your file if the condition is true.
| | 4 | No.4 Revision |
Does that mean, that a subscriber in ROS HAS to CONTINUOUSLY listen to the topic being published? What if I don't want to? What if I want to listen to a topic say, only when 'flag' is set to 1?
In short: no, you don't have to, you can (re)subscribe and unsubscribe at any time. Subscription you know (NodeHandle::subscribe(..)), to stop a subscription, use NodeHandleSubscriber::shutdown(). Now subscribe on flag == 1, then shutdown on flag == 0. Keep in mind that it can take some time for your subscription to be processed (as was already mentioned by @Lorenz in your other question).
Instead of (re|un)subscribing, you could also check for flag == 1 in your callback, and only write to your file if the condition is true.
It just bothers me that ROS being such an amazing platform, does not seem to have a simple solution to intermittent/'at will' subscription to a topic!
It does, internally there is no difference between a 'temporary' subscription and a 'for-the-duration-of-the-program' subscription. It's just up to you to manage your subscriptions properly.
ROS Answers is licensed under Creative Commons Attribution 3.0 Content on this site is licensed under a Creative Commons Attribution Share Alike 3.0 license.
