ROS message callback function

asked 2020-07-17 14:00:53 -0600

Chao Chen
56 ●21 ●31 ●29

updated 2020-07-19 18:44:58 -0600

4203 ●18 ●103 ●63

My code subscribes to a customized rosmsg "/lcm_to_ros/leg_corol_data" by doing ros::Subscriber sub = n.subscribe("/lcm_to_ros/leg_corol_data", 1000, legCallback); This Rosmsg has a type of "leg_control_data_lcmt"

How to write the correct callback function? callback function works for msg type"std_msgs/String.h", but not for the class "leg_control_data_lcmt" I created.

The callback function fails because of the rosmsg type "leg_control_data_lcmt" imported from "leg_control_data_lcmt.hpp". I wonder how to handle customized rosmsg in callback function??

void legCallback(const leg_control_data_lcmt* msg)
{
 ROS_INFO("test");
}

The error is like this. Is it because I did not include callback function in Cmakefile. How can I do this ?

In file included from /opt/ros/kinetic/include/ros/serialization.h:37:0,
                 from /opt/ros/kinetic/include/ros/publisher.h:34,
                 from /opt/ros/kinetic/include/ros/node_handle.h:32,
                 from /opt/ros/kinetic/include/ros/ros.h:45,
                 from /home/chao/catkin_ws/src/new_joint_pub/src/state_publisher.cpp:2:
/opt/ros/kinetic/include/ros/message_traits.h: In instantiation of ‘static const char* ros::message_traits::MD5Sum<M>::value() [with M = leg_control_data_lcmt]’:
/opt/ros/kinetic/include/ros/message_traits.h:228:102:   required from ‘const char* ros::message_traits::md5sum() [with M = leg_control_data_lcmt]’
/opt/ros/kinetic/include/ros/subscribe_options.h:89:49:   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 = const leg_control_data_lcmt&; std::__cxx11::string = std::__cxx11::basic_string<char>; uint32_t = unsigned int; typename ros::ParameterAdapter<P>::Message = leg_control_data_lcmt]’
/opt/ros/kinetic/include/ros/node_handle.h:406:5:   required from ‘ros::Subscriber ros::NodeHandle::subscribe(const string&, uint32_t, void (T::*)(M), T*, const ros::TransportHints&) [with M = const leg_control_data_lcmt&; T = SubscribeAndPublish; std::__cxx11::string = std::__cxx11::basic_string<char>; uint32_t = unsigned int]’
/home/chao/catkin_ws/src/new_joint_pub/src/state_publisher.cpp:17:94:   required from here
/opt/ros/kinetic/include/ros/message_traits.h:121:28: error: ‘__s_getMD5Sum’ is not a member of ‘leg_control_data_lcmt’
     return M::__s_getMD5Sum().c_str();
                            ^
/opt/ros/kinetic/include/ros/message_traits.h: In instantiation of ‘static const char* ros::message_traits::DataType<M>::value() [with M = leg_control_data_lcmt]’:
/opt/ros/kinetic/include/ros/message_traits.h:237:104:   required from ‘const char* ros::message_traits::datatype() [with M = leg_control_data_lcmt]’
/opt/ros/kinetic/include/ros/subscribe_options.h:90:53:   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 = const leg_control_data_lcmt&; std::__cxx11::string = std::__cxx11::basic_string<char>; uint32_t = unsigned int; typename ros::ParameterAdapter<P>::Message = leg_control_data_lcmt]’
/opt/ros/kinetic/include/ros/node_handle.h:406:5:   required from ‘ros::Subscriber ros::NodeHandle::subscribe(const string&, uint32_t, void (T::*)(M), T*, const ros::TransportHints&) [with M = const leg_control_data_lcmt&; T = SubscribeAndPublish; std::__cxx11::string = std::__cxx11::basic_string<char>; uint32_t = unsigned int]’
/home/chao/catkin_ws/src/new_joint_pub/src/state_publisher.cpp:17:94:   required from here
/opt/ros/kinetic/include/ros/message_traits.h:138:30: error: ‘__s_getDataType’ is not a member of ‘leg_control_data_lcmt’
     return M::__s_getDataType().c_str();
                              ^
In file included from /opt/ros/kinetic/include/ros/publisher.h:34:0,
                 from /opt/ros/kinetic/include/ros/node_handle.h ...

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answered 2020-07-19 06:00:20 -0600

Weasfas
1695 ●12 ●91 ●41

You may want to check this and this. The first link explain you how to implement a custom msg and the second how to use it in a subscriber. You forgot the namespace: your_package_msg::leg_control_data_lcmt and the proper definition of the argument in the callback:

void legCallback (const your_package_msg::leg_control_data_lcmt::ConstPtr &msg) { ROS_INFO("test"); }

Also you need to take into accout the proper cmake instructions to generate your messages bindings and package dependencies. Finally please remember to include your message bindings header in your code, like:

#include <your_package_msg/leg_control_data_lcmt.h>

Hope that solve your problem.

Regards.

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The header to include and the namespace/type name to use for your custom message type are shown in this tutorial about defining custom messages.

Geoff ( 2020-07-19 18:45:59 -0600 )edit

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ROS message callback function

How to write the correct callback function? callback function works for msg type"std_msgs/String.h", but not for the class "leg_control_data_lcmt" I created.

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How to write the correct callback function? callback function works for msg type"std_msgs/String.h", but not for the class "leg_control_data_lcmt" I created.

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ROS message callback function