C++で簡単な購読者を書く

cd ~/catkin_ws/src/beginner_tutorials

vim src/listener.cpp

#include "ros/ros.h"

#include "std_msgs/String.h"



/**

 * This tutorial demonstrates simple receipt of messages over the ROS system.

 */

void chatterCallback(const std_msgs::String::ConstPtr& msg)

{

  ROS_INFO("I heard: [%s]", msg->data.c_str());

}



int main(int argc, char **argv)

{

  /**

   * The ros::init() function needs to see argc and argv so that it can perform

   * any ROS arguments and name remapping that were provided at the command line. For programmatic

   * remappings you can use a different version of init() which takes remappings

   * directly, but for most command-line programs, passing argc and argv is the easiest

   * way to do it.  The third argument to init() is the name of the node.

   *

   * You must call one of the versions of ros::init() before using any other

   * part of the ROS system.

   */

  ros::init(argc, argv, "listener");



  /**

   * NodeHandle is the main access point to communications with the ROS system.

   * The first NodeHandle constructed will fully initialize this node, and the last

   * NodeHandle destructed will close down the node.

   */

  ros::NodeHandle n;



  /**

   * The subscribe() call is how you tell ROS that you want to receive messages

   * on a given topic.  This invokes a call to the ROS

   * master node, which keeps a registry of who is publishing and who

   * is subscribing.  Messages are passed to a callback function, here

   * called chatterCallback.  subscribe() returns a Subscriber object that you

   * must hold on to until you want to unsubscribe.  When all copies of the Subscriber

   * object go out of scope, this callback will automatically be unsubscribed from

   * this topic.

   *

   * The second parameter to the subscribe() function is the size of the message

   * queue.  If messages are arriving faster than they are being processed, this

   * is the number of messages that will be buffered up before beginning to throw

   * away the oldest ones.

   */

  ros::Subscriber sub = n.subscribe("chatter", 1000, chatterCallback);



  /**

   * ros::spin() will enter a loop, pumping callbacks.  With this version, all

   * callbacks will be called from within this thread (the main one).  ros::spin()

   * will exit when Ctrl-C is pressed, or the node is shutdown by the master.

   */

  ros::spin();



  return 0;

}

void chatterCallback(const std_msgs::String::ConstPtr& msg)

{

  ROS_INFO("I heard: [%s]", msg->data.c_str());

}

ros::Subscriber sub = n.subscribe("chatter", 1000, chatterCallback);

ros::spin();

cmake_minimum_required(VERSION 2.8.3)

project(beginner_tutorials)



## Find catkin and any catkin packages

find_package(catkin REQUIRED COMPONENTS roscpp rospy std_msgs genmsg)



## Declare ROS messages and services

add_message_files(DIRECTORY msg FILES Num.msg)

add_service_files(DIRECTORY srv FILES AddTwoInts.srv)



## Generate added messages and services

generate_messages(DEPENDENCIES std_msgs)



## Declare a catkin package

catkin_package()

cmake_minimum_required(VERSION 2.8.3)

project(beginner_tutorials)



## Find catkin and any catkin packages

find_package(catkin REQUIRED COMPONENTS roscpp rospy std_msgs genmsg)



## Declare ROS messages and services

add_message_files(FILES Num.msg)

add_service_files(FILES AddTwoInts.srv)



## Generate added messages and services

generate_messages(DEPENDENCIES std_msgs)



## Declare a catkin package

catkin_package()



## Build talker and listener

include_directories(include ${catkin_INCLUDE_DIRS})



add_executable(talker src/talker.cpp)

target_link_libraries(talker ${catkin_LIBRARIES})

add_dependencies(talker beginner_tutorials_generate_messages_cpp)



add_executable(listener src/listener.cpp)

target_link_libraries(listener ${catkin_LIBRARIES})

add_dependencies(listener beginner_tutorials_generate_messages_cpp)

catkin_make