Publish and subscribe array of vector as message

edit

Hello,

I've created a new message to do that, including an array and another field, just to show how you can do that.

The command to create the package: catkin_create_pkg my_pkg roscpp std_msgs geometry_msgs

The message definition (my_pkg/msg/my_msg.msg)

geometry_msgs/Point[] points
uint8 another_field

In the my_pkg/package.xml file, don't forget to add the dependencies for generating the messages:

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

my_pkg/CMakeLists.txt file:

cmake_minimum_required(VERSION 2.8.3)
project(my_pkg)

find_package(catkin REQUIRED COMPONENTS
  geometry_msgs
  roscpp
  std_msgs
  message_generation
)

## Generate messages in the 'msg' folder
add_message_files(
  FILES
  my_msg.msg
#   Message2.msg
)

## Generate added messages and services with any dependencies listed here
generate_messages(
  DEPENDENCIES
  geometry_msgs#   std_msgs
)

catkin_package(
#  INCLUDE_DIRS include
#  LIBRARIES my_pkg
   CATKIN_DEPENDS geometry_msgs roscpp std_msgs message_runtime
#  DEPENDS system_lib
)

include_directories(
  ${catkin_INCLUDE_DIRS}
)

add_executable(my_publisher src/my_publisher.cpp)
add_executable(my_subscriber src/my_subscriber.cpp)

add_dependencies(my_publisher ${${PROJECT_NAME}_EXPORTED_TARGETS} ${catkin_EXPORTED_TARGETS})
add_dependencies(my_subscriber ${${PROJECT_NAME}_EXPORTED_TARGETS} ${catkin_EXPORTED_TARGETS})

target_link_libraries(my_publisher ${catkin_LIBRARIES})
target_link_libraries(my_subscriber ${catkin_LIBRARIES})

Finally, the publisher and subscriber files:

my_pkg/src/my_publisher.cpp

#include "ros/ros.h"
#include "geometry_msgs/Point.h"
#include "my_pkg/my_msg.h"

#include <vector>

struct Point {
    float x;
    float y;
};

int main(int argc, char **argv)
{
  // ROS objects
  ros::init(argc, argv, "my_publisher");
  ros::NodeHandle n;
  ros::Publisher pub = n.advertise<my_pkg::my_msg>("my_topic", 1);
  ros::Rate loop_rate(0.5);

  // the message to be published
  my_pkg::my_msg msg;
  msg.another_field = 0;

  // creating the vector
  Point my_array[11];
  Point point;
  for (int i=0; i < 11; i++) {
    point.x = i;
    point.y = i;
    my_array[i] = point;
  }
  std::vector<Point> my_vector (my_array, my_array + sizeof(my_array) / sizeof(Point));

  // loop control
  int count = 0;
  while (ros::ok())
  {
    msg.points.clear();

    msg.another_field = count;
    int i = 0;
    for (std::vector<Point>::iterator it = my_vector.begin(); it != my_vector.end(); ++it) {
        geometry_msgs::Point point;
        point.x = (*it).x;
        point.y = (*it).y;
        point.z = 0;
        msg.points.push_back(point);
        i++;
    }

    ROS_INFO("%d", msg.another_field);

    pub.publish(msg);

    ros::spinOnce();

    loop_rate.sleep();
    ++count;
  }


  return 0;
}

my_pkg/src/my_subscriber.cpp

#include "ros/ros.h"
#include "my_pkg/my_msg.h"

void clbk(const my_pkg::my_msg::ConstPtr& msg) {
    ROS_INFO("%d", msg->another_field);
    ROS_INFO("first point: x=%.2f, y=%.2f", msg->points[0].x, msg->points[0].y);
}

int main(int argc, char **argv)
{
  // ROS objects
  ros::init(argc, argv, "my_subscriber");
  ros::NodeHandle n;
  ros::Subscriber sub = n.subscribe("my_topic", 1, clbk);

  ros::spin();

}

If you want to see step-by-step, I've created a video ( https://youtu.be/4eHWSXGqXg8 ).