ROS custom message publishing subscription example

ROS Example of custom message publishing and subscription

This paper mainly explains from the following aspects ：

• 1. Create custom msg news
• 2. Release msg - Other packages call customization msg type
• 3. Subscription customization msg

1. Create custom msg news

First create an empty package Separate storage msg type （ Of course, it can also be in any package Custom in msg type ）
For the convenience of explanation , Create a wts_rviz_msgs My bag , Used to customize msg Examples of usage of types .

$ cd catkin_ws/src  // This is just an example , It is actually the project root directory （src、devel Under the same category ）
$ catkin_create_pkg wts_rviz_msgs 

1.1. newly build msg file

stay wts_rviz_msgs Created in msg Folder , stay msg Create the following message type file in the folder ：

• PointInfo.msg
• ParkingSpot.msg
• ParkingSpotList.msg

$ cd wts_rviz_msgs
$ mkdir msg

For basic types, please refer to :

• common_msgs – http://wiki.ros.org/common_msgs
• std_msgs – http://wiki.ros.org/std_msgs

PointInfo.msg Content ：

float32 dPointX
float32 dPointY

ParkingSpot.msg Content ：

string parking_spot_name
bool publish_state
geometry_msgs/Pose2D pose
PointInfo[] point_list

ParkingSpotList.msg Content ：

ParkingSpot[] parking_spot_list

1.2. modify package.xml

need message_generation Generate C++ or Python Usable code , need message_runtime Provide runtime support , therefore package.xml Add the following two sentences

ROS1 in ：

<build_depend>message_generation</build_depend>
<run_depend>message_runtime</run_depend>

ROS2 in ：

<build_depend>message_generation</build_depend>
<exec_depend>message_runtime</exec_depend>

1.3. modify CMakeLists.txt

CMakeLists.txt Pay attention to four places

(1) Set up find_package

 First call  find_package  Find dependent packages , Necessary are roscpp rospy message_generation, Others are added according to specific types , Like the one above msg The document uses geometry_msgs/Pose pose type , Then you must find geometry_msgs

find_package(catkin REQUIRED COMPONENTS roscpp rospy message_generation std_msgs geometry_msgs)

(2) Set up add_message_files

  And then there was  add_message_files , Appoint msg file 

add_message_files(
  FILES
  PointInfo.msg
  ParkingSpot.msg
  ParkingSpotList.msg
)

(3) Set up generate_messages

And then there was generate_messages , Specify the dependencies when generating the message file , For example, other message types are nested above geometry_msgs, Then you must indicate

#generate_messages Must be in catkin_package front 
generate_messages(
 DEPENDENCIES
 std_msgs
 geometry_msgs
)

(4) Set up catkin_package
And then there was catkin_package Set run dependency

catkin_package(

CATKIN_DEPENDS message_runtime

)

(5) compile

$ cd catkin_ws  // This is just an example , It is actually the project root directory （src、devel Under the same category ）
$ catkin_make -j4

(6) see rosmsg

New here msg type wts_rviz_msgs/ParkingSpotList You can use it , Now compile this package , And then use it rosmsg show Command view .

$ cd  Project root   // And devel At the same directory 
$ source devel/setup.bash    # Be careful ： Must be implemented source  Installation , Otherwise, the message will not be recognized 
$ rosmsg show  wts_rviz_msgs/ParkingSpotList 

2. Release msg - Other packages call customization msg type

To use a custom message type, you must source Customize the workspace where the message is located , otherwise rosmsg show wts_rviz_msgs/ParkingSpotList t and rostopic echo /wts_topic_rviz_msgs(/wts_rviz_msgs Is the custom message type used in the node wts_rviz_msgs/ParkingSpotList Of topic) All will report wrong. , Because no source In this case, the custom message type is invisible , Is considered an undefined type

A typical mistake is to delete devel and build Folder and recompile the code , At this time, because there is no source Customize the workspace where the message is located , Even if the code using the custom message and the custom message are in the same package, they cannot be found , The header file , You need to run source devel/setup.bash Then recompile it .

If it's in test_msgs Call... From the node in the package test_msgs/Test type , Only need .cpp Call the following in the file

#include "wts_rviz_msgs/ParkingSpotList.h"


wts_rviz_msgs::ParkingSpotList  msg_parking_spot_list_published;

If it is called in other packages wts_rviz_msgs/ParkingSpotList Type needs to be modified package.xml and CMakeLists.txt, For example, in the workspace catkin_ws There is a named interactive_parking_spot My bag , We can write a node in this package , Use the message type we just customized wts_rviz_msgs/ParkingSpotList , as follows ：

**(1) modify package.xml **

Develop good habits , Maintain the update of software package list , So that others can install various dependencies before using your software , Of course, this file does not affect program compilation

ROS1 in ：

<build_depend>roscpp</build_depend>
<run_depend>roscpp</run_depend>

<build_depend>wts_rviz_msgs</build_depend>
<run_depend>wts_rviz_msgs</run_depend>

ROS2 in ：

<build_depend>roscpp</build_depend>
<run_depend>roscpp</run_depend>

 <build_depend>wts_rviz_msgs</build_depend>
    <exec_depend>wts_rviz_msgs</exec_depend>

**(2) modify CMakeLists.txt **

Calling a custom message type mainly modifies two places , Here's the point ：
One is find_package You need to declare to find the package containing this message type ;
Two is add_dependencies Note the dependence of the message , Other places are the same as ordinary nodes

#： Be careful , Because  geometry_msgs/Pose2D  type , The compiled version requires   Greater than  C++11
add_compile_options(-std=c++17)

find_package(catkin REQUIRED COMPONENTS
  roscpp
  geometry_msgs
  wts_rviz_msgs
)

add_executable(interactive_parking_spot src/main.cpp)
target_link_libraries(interactive_parking_spot
   ${catkin_LIBRARIES}
)

# When calling a custom message type in the same workspace, indicate the dependency , Prevent the error that the header file cannot be found 
add_dependencies(interactive_parking_spot wts_rviz_msgs_gencpp)

If there is a lack of add_dependencies Chinese vs wts_rviz_msgs_gencpp A dependency statement for , When compiling, if you compile first interactive_parking_spot Package recompilation wts_rviz_msgs/ParkingSpotList The following error will appear in the package （ROS The compilation order of each software package in the workspace is random ）, Because the header file wts_rviz_msgs/ParkingSpotList.h Not generated yet

fatal error: wts_rviz_msgs/ParkingSpotList.h: There is no file or directory
#include “wts_rviz_msgs/ParkingSpotList.h”

2.1. Write message publishing code : src/main.cpp

#include "wts_rviz_msgs/ParkingSpotList.h"


int main(int argc, char** argv)
{
  ros::init(argc, argv, "simple_marker");
  
 ros::NodeHandle n;
  ros::Publisher chatter_pub = n.advertise<wts_rviz_msgs::ParkingSpotList>("wts_topic_msg_parking_spots_info", 1000);
  ros::Rate loop_rate(1);



  while(ros::ok())
  {
    int iNum = parkingSpot.m_mapParkingSpot.size();


    wts_rviz_msgs::ParkingSpotList msg_parking_spot_list_published;
    std::map<std::string, WtsRvizParkingSpot>::iterator iter;
    int iIndex = 0;
    for(iter = parkingSpot.m_mapParkingSpot.begin(); iter!=parkingSpot.m_mapParkingSpot.end(); iter++)
    {

      wts_rviz_msgs::ParkingSpot parking_spot;
      parking_spot.parking_spot_name = "ParkingSpotName";
      parking_spot.publish_state = true
      parking_spot.pose.x = 2.0082790851593018;
      parking_spot.pose.x = 0;
      parking_spot.pose.theta = 0.7217559218406677;
      for(int iIndex = 0; iIndex < iter->second.vctrParkingSpotPoints.size(); iIndex++)
      {
        wts_rviz_msgs::PointInfo point_info;
        point_info.dPointX = -1.6596179008483887;
        point_info.dPointY = 2.2936594486236572;
        parking_spot.point_list.push_back(point_info);
      }

      msg_parking_spot_list_published.parking_spot_list.push_back(parking_spot);

      iIndex++;
    }


    chatter_pub.publish(msg_parking_spot_list_published);

    ros::spinOnce();
    loop_rate.sleep();
  }

}

3. Subscription customization msg

Create a new accept message node mylisten.cpp, Add the following code ：bash

#include <ros/ros.h>
#include <geometry_msgs/Pose2D.h>
#include "wts_rviz_msgs/ParkingSpotList.h"

void msgCallback(const wts_rviz_msgs::ParkingSpotList::ConstPtr &P)
{
  ROS_INFO("I recevied the topic: ");
  for(std::vector<wts_rviz_msgs::ParkingSpotList>::const_iterator it = P->path.begin(); it != P->path.end(); ++it)
  {
     //... ...
  }
}

int main(int argc,char ** argv)
{
  ros::init(argc,argv,"test1");
  ros::NodeHandle n;

  ros::Subscriber msg_sub = n.subscribe("wts_topic_msg_parking_spots_info", 100, msgCallback);

  ros::spin();
  return 0;
}

Follow the previous release msg An example of , modify CMakeLists.txt、package.xml, Then catkin_make Recompile , Just OK 了 .