Subscribing to nav_msgs::Path message

asked 2018-11-19 13:28:37 -0600

kllysin
13 ●6 ●8 ●9

updated 2018-11-19 13:30:47 -0600

Hi everyone,

I am trying to subscribe to a message of type nav_msgs::Path. Following is the callback function:

    nav_msgs::Path gPlan;
    void planCallback(nav_msgs::Path::ConstPtr& msg)
    {
         int i=0;
          for(std::vector<geometry_msgs::PoseStamped>::const_iterator it= msg->poses.begin(); it!= msg->poses.end();  ++it)
          {

              gPlan.poses[i] = *it;
              i++;
           }
      }

The subscriber has been defined as:

ros::Subscriber planSub = n.subscribe("global_plan", 1000, planCallback);

The error I am getting is as follows:

In file included from /opt/ros/indigo/include/ros/serialization.h:37:0,
                 from /opt/ros/indigo/include/ros/publisher.h:34,
                 from /opt/ros/indigo/include/ros/node_handle.h:32,
                 from /opt/ros/indigo/include/ros/ros.h:45,
                 from /home/lead/catkin_ws_autoware/src/PPpublisher/src/purepursuitPub.cpp:1:
/opt/ros/indigo/include/ros/message_traits.h: In instantiation of ‘static const char* ros::message_traits::MD5Sum<M>::value() [with M = boost::shared_ptr<const nav_msgs::Path_<std::allocator<void> > >]’:
/opt/ros/indigo/include/ros/message_traits.h:228:103:   required from ‘const char* ros::message_traits::md5sum() [with M = boost::shared_ptr<const nav_msgs::Path_<std::allocator<void> > >]’
/opt/ros/indigo/include/ros/subscribe_options.h:89:50:   required from ‘void ros::SubscribeOptions::initByFullCallbackType(const string&, uint32_t, const boost::function<void(P)>&, const boost::function<boost::shared_ptr<typename ros::ParameterAdapter<P>::Message>()>&) [with P = boost::shared_ptr<const nav_msgs::Path_<std::allocator<void> > >&; std::string = std::basic_string<char>; uint32_t = unsigned int; typename ros::ParameterAdapter<P>::Message = boost::shared_ptr<const nav_msgs::Path_<std::allocator<void> > >]’
/opt/ros/indigo/include/ros/node_handle.h:658:5:   required from ‘ros::Subscriber ros::NodeHandle::subscribe(const string&, uint32_t, void (*)(M), const ros::TransportHints&) [with M = boost::shared_ptr<const nav_msgs::Path_<std::allocator<void> > >&; std::string = std::basic_string<char>; uint32_t = unsigned int]’
/home/lead/catkin_ws_autoware/src/PPpublisher/src/purepursuitPub.cpp:71:74:   required from here
/opt/ros/indigo/include/ros/message_traits.h:121:29: error: ‘__s_getMD5Sum’ is not a member of ‘boost::shared_ptr<const nav_msgs::Path_<std::allocator<void> > >’
     return M::__s_getMD5Sum().c_str();
                             ^
/opt/ros/indigo/include/ros/message_traits.h: In instantiation of ‘static const char* ros::message_traits::DataType<M>::value() [with M = boost::shared_ptr<const nav_msgs::Path_<std::allocator<void> > >]’:
/opt/ros/indigo/include/ros/message_traits.h:237:105:   required from ‘const char* ros::message_traits::datatype() [with M = boost::shared_ptr<const nav_msgs::Path_<std::allocator<void> > >]’
/opt/ros/indigo/include/ros/subscribe_options.h:90:54:   required from ‘void ros::SubscribeOptions::initByFullCallbackType(const string&, uint32_t, const boost::function<void(P)>&, const boost::function<boost::shared_ptr<typename ros::ParameterAdapter<P>::Message>()>&) [with P = boost::shared_ptr<const nav_msgs::Path_<std::allocator<void> > >&; std::string = std::basic_string<char>; uint32_t = unsigned int; typename ros::ParameterAdapter<P>::Message = boost::shared_ptr<const nav_msgs::Path_<std::allocator<void> > >]’
/opt/ros/indigo/include/ros/node_handle.h:658:5:   required from ‘ros::Subscriber ros::NodeHandle::subscribe(const string&, uint32_t, void (*)(M), const ros::TransportHints&) [with M = boost::shared_ptr<const nav_msgs::Path_<std::allocator<void> > >&; std::string = std::basic_string<char>; uint32_t = unsigned int]’
/home/lead/catkin_ws_autoware/src/PPpublisher/src/purepursuitPub.cpp:71:74:   required from here
/opt/ros/indigo ...

(more)

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answered 2018-11-19 13:47:40 -0600

PeteBlackerThe3rd

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If you just want to create a copy of the path message, then the copy constructors mean you can do this:

gPlan = nav_msgs::Path(msg);

Hope this helps.

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Thanks for your answer!

kllysin ( 2018-11-19 14:47:01 -0600 )edit

Thanks, @PeteBlackerThe3rd, it worked like a charm!

MichelleHusbands ( 2020-11-12 18:36:29 -0600 )edit

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answered 2018-11-19 14:47:47 -0600

kllysin
13 ●6 ●8 ●9

Adding the solution I figured out. I changed the callback function to:

void planCallback(const nav_msgs::Path::ConstPtr& msg) { int i=0; std::vector<geometry_msgs::posestamped> data = msg->poses; for(std::vector<geometry_msgs::posestamped>::const_iterator it= data.begin(); it!= data.end(); ++it) { //gPlan.poses.header.stamp = gPlan.poses[i].header = it->header; gPlan.poses[i].pose = it->pose; i++; } }

and it works.

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This may work some of the time. But you're doing something really bad here You're writing data into gPlan.poses beyond what's allocated, risking a segfault. You should use the push_back() method or pre-allocate it first.

PeteBlackerThe3rd ( 2018-11-19 16:26:19 -0600 )edit

@kllysin, could you please copy your code again in a correct format? Because, now its not able to read properly. I am also trying something like you. I need to take the position info of X and Y from the nav_msgs/Path. Please help me . I have information about two waypoints in the topic named "cmd_local_waypoints" I need to take the x and y positions (two x and y s) out.

Thanks in advance

manuelmelvin ( 2019-03-22 18:38:17 -0600 )edit

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Subscribing to nav_msgs::Path message

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