创建订阅者代码(C++)
如何实现一个订阅者
*初始化ROS节点;
*订阅需要的话题;
*循环等待话题消息,接受到消息后进入回调函数;
*在回调函数中完成消息处理.

//创建cpp文件
cd learning_topic/src/
touch velocity_publisher.cpp

//代码
/**
 * 该例程将订阅/turtle1/pose话题，消息类型turtlesim::Pose
 */
 
#include <ros/ros.h>
#include "turtlesim/Pose.h"

// 接收到订阅的消息后，会进入消息回调函数
void poseCallback(const turtlesim::Pose::ConstPtr& msg)
{
    // 将接收到的消息打印出来
    ROS_INFO("Turtle pose: x:%0.6f, y:%0.6f", msg->x, msg->y);
}

int main(int argc, char **argv)
{
    // 初始化ROS节点
    ros::init(argc, argv, "pose_subscriber");

    // 创建节点句柄
    ros::NodeHandle n;

    // 创建一个Subscriber，订阅名为/turtle1/pose的topic，注册回调函数poseCallback
    ros::Subscriber pose_sub = n.subscribe("/turtle1/pose", 10, poseCallback);

    // 循环等待回调函数
    ros::spin();

    return 0;
}

编译并运行订阅者

//配置CMakeLists.txt
add_executable(pose_subscriber src/pose_subscriber.cpp)
target_link_libraries(pose_subscriber ${catkin_LIBRARIES})
//编译并运行
cd ~/catkin_ws
catkin_make
source devel/setup.bash
roscore
//新开一个终端，开启turtlesim
rosrun turtlesim turtlesim_node
//新开一个终端，运行发布者cpp程序
rosrun learning_topic pose_subscriber

#!/usr/bin/env python
# -*- coding: utf-8 -*-
# 该例程将订阅/turtle1/pose话题，消息类型turtlesim::Pose

import rospy
from turtlesim.msg import Pose

def poseCallback(msg):
    rospy.loginfo("Turtle pose: x:%0.6f, y:%0.6f", msg.x, msg.y)

def pose_subscriber():
    # ROS节点初始化
    rospy.init_node('pose_subscriber', anonymous=True)

    # 创建一个Subscriber，订阅名为/turtle1/pose的topic，注册回调函数poseCallback
    rospy.Subscriber("/turtle1/pose", Pose, poseCallback)

    # 循环等待回调函数
    rospy.spin()

if __name__ == '__main__':
    pose_subscriber()