Package for Generically Listening to Topics

asked 2014-01-13 04:32:15 -0600

orion
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updated 2014-01-14 09:45:03 -0600

Is there a way to get a list of topics while running a node. For example, if a new message is published, is there a way to programmatically get the topic name posted (equivalent to running rostopic list in a terminal).

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answered 2014-01-13 05:00:48 -0600

dornhege

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I used this to add topics of a certain type to a GUI selector:

ros::master::V_TopicInfo ti;
if(ros::master::getTopics(ti)) {
    for(ros::master::V_TopicInfo::iterator it = ti.begin(); it != ti.end(); it++) {
        if(it->datatype == _topicType)
            ui.topicsList->addItem(it->name.c_str());
    }
}

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Looks good to me. I will try it and see if it works for my needs. However, I may also need to do this in python. I figured before I start digging I could ask if you knew of a solution for that as well?

orion ( 2014-01-14 09:45:53 -0600 )edit

Yes and no: I don't have code, but there are python APIs that do exactly the same thing. If you can't find that easily in the rospy documentation, just see what rostopic list does.

dornhege ( 2014-01-15 00:47:49 -0600 )edit

So I setup and have the ability to get topics whether it be C++ or python. I started looking further through the code to see if there was a way to listen for a new topic as a callback (similar to subscriber), versus a ROS loop, but did not see one. Curious if I just missed it?

orion ( 2014-02-11 06:47:15 -0600 )edit

You want something that tells you if a new topic has come up? I don't think that exists. So you'd probably need to keep polling.

dornhege ( 2014-02-11 22:17:29 -0600 )edit

That is what I assumed. I just made a polling method to take care of it. Thanks.

orion ( 2014-02-15 07:55:37 -0600 )edit

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answered 2018-05-16 04:00:04 -0600

Markus
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updated 2018-05-16 04:18:54 -0600

You can also try this code :)

ros::master::V_TopicInfo master_topics;
ros::master::getTopics(master_topics);

for (ros::master::V_TopicInfo::iterator it = master_topics.begin() ; it != master_topics.end(); it++) {
    const ros::master::TopicInfo& info = *it;
    std::cout << "Topic : " << it - master_topics.begin() << ": " << info.name << " -> " << info.datatype <<       std::endl;
}

However if someone knows how to do that with rospy let me know ! :)

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Package for Generically Listening to Topics

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