【ROS2指南-12】编写一个简单的发布者和订阅者

1 创建一个包

打开一个新终端并 source，这样ros2命令就可以工作了。

导航到在上一教程 dev_ws 中创建的目录。

回想一下，应该在src目录中创建包，而不是在工作空间的根目录中。因此，导航到 dev_ws/src并运行包创建命令：

ros2 pkg create --build-type ament_cmake cpp_pubsub

wget -O publisher_member_function.cpp https://raw.githubusercontent.com/ros2/examples/dashing/rclcpp/minimal_publisher/member_function.cpp

#include <chrono>
#include <functional>
#include <memory>
#include <string>#include "rclcpp/rclcpp.hpp"
#include "std_msgs/msg/string.hpp"using namespace std::chrono_literals;/* This example creates a subclass of Node and uses std::bind() to register a
* member function as a callback from the timer. */class MinimalPublisher : public rclcpp::Node
{public:MinimalPublisher(): Node("minimal_publisher"), count_(0){publisher_ = this->create_publisher<std_msgs::msg::String>("topic", 10);timer_ = this->create_wall_timer(500ms, std::bind(&MinimalPublisher::timer_callback, this));}private:void timer_callback(){auto message = std_msgs::msg::String();message.data = "Hello, world! " + std::to_string(count_++);RCLCPP_INFO(this->get_logger(), "Publishing: '%s'", message.data.c_str());publisher_->publish(message);}rclcpp::TimerBase::SharedPtr timer_;rclcpp::Publisher<std_msgs::msg::String>::SharedPtr publisher_;size_t count_;
};int main(int argc, char * argv[])
{rclcpp::init(argc, argv);rclcpp::spin(std::make_shared<MinimalPublisher>());rclcpp::shutdown();return 0;
}

#include <chrono>
#include <functional>
#include <memory>
#include <string>#include "rclcpp/rclcpp.hpp"
#include "std_msgs/msg/string.hpp"using namespace std::chrono_literals;

class MinimalPublisher : public rclcpp::Node

public:MinimalPublisher(): Node("minimal_publisher"), count_(0){publisher_ = this->create_publisher<std_msgs::msg::String>("topic", 10);timer_ = this->create_wall_timer(500ms, std::bind(&MinimalPublisher::timer_callback, this));}

private:void timer_callback(){auto message = std_msgs::msg::String();message.data = "Hello, world! " + std::to_string(count_++);RCLCPP_INFO(this->get_logger(), "Publishing: '%s'", message.data.c_str());publisher_->publish(message);}

rclcpp::TimerBase::SharedPtr timer_;
rclcpp::Publisher<std_msgs::msg::String>::SharedPtr publisher_;
size_t count_;

int main(int argc, char * argv[])
{rclcpp::init(argc, argv);rclcpp::spin(std::make_shared<MinimalPublisher>());rclcpp::shutdown();return 0;
}

<description>Examples of minimal publisher/subscriber using rclcpp</description>
<maintainer email="you@email.com">Your Name</maintainer>
<license>Apache License 2.0</license>

<depend>rclcpp</depend>
<depend>std_msgs</depend>

add_executable(talker src/publisher_member_function.cpp)
ament_target_dependencies(talker rclcpp std_msgs)

install(TARGETStalkerDESTINATION lib/${PROJECT_NAME})

cmake_minimum_required(VERSION 3.5)
project(cpp_pubsub)#Default to C++14
if(NOT CMAKE_CXX_STANDARD)set(CMAKE_CXX_STANDARD 14)
endif()if(CMAKE_COMPILER_IS_GNUCXX OR CMAKE_CXX_COMPILER_ID MATCHES "Clang")add_compile_options(-Wall -Wextra -Wpedantic)
endif()find_package(ament_cmake REQUIRED)
find_package(rclcpp REQUIRED)
find_package(std_msgs REQUIRED)add_executable(talker src/publisher_member_function.cpp)
ament_target_dependencies(talker rclcpp std_msgs)install(TARGETStalkerDESTINATION lib/${PROJECT_NAME})ament_package()

您现在可以构建您的程序包，获取本地设置文件并运行它，但让我们先创建订阅者节点，以便您可以看到整个系统在工作。

wget -O subscriber_member_function.cpp https://raw.githubusercontent.com/ros2/examples/dashing/rclcpp/minimal_subscriber/member_function.cpp

publisher_member_function.cpp  subscriber_member_function.cpp

#include <memory>#include "rclcpp/rclcpp.hpp"
#include "std_msgs/msg/string.hpp"
using std::placeholders::_1;class MinimalSubscriber : public rclcpp::Node
{public:MinimalSubscriber(): Node("minimal_subscriber"){subscription_ = this->create_subscription<std_msgs::msg::String>("topic", 10, std::bind(&MinimalSubscriber::topic_callback, this, _1));}private:void topic_callback(const std_msgs::msg::String::SharedPtr msg) const{RCLCPP_INFO(this->get_logger(), "I heard: '%s'", msg->data.c_str());}rclcpp::Subscription<std_msgs::msg::String>::SharedPtr subscription_;
};int main(int argc, char * argv[])
{rclcpp::init(argc, argv);rclcpp::spin(std::make_shared<MinimalSubscriber>());rclcpp::shutdown();return 0;
}

public:MinimalSubscriber(): Node("minimal_subscriber"){subscription_ = this->create_subscription<std_msgs::msg::String>("topic", 10, std::bind(&MinimalSubscriber::topic_callback, this, _1));}

private:void topic_callback(const std_msgs::msg::String::SharedPtr msg) const{RCLCPP_INFO(this->get_logger(), "I heard: '%s'", msg->data.c_str());}rclcpp::Subscription<std_msgs::msg::String>::SharedPtr subscription_;

确保保存文件，然后您的发布/订阅系统就可以使用了。

rosdep install -i --from-path src --rosdistro <distro> -y

colcon build --packages-select cpp_pubsub

. install/setup.bash

ros2 run cpp_pubsub talker

[INFO] [minimal_publisher]: Publishing: "Hello World: 0"
[INFO] [minimal_publisher]: Publishing: "Hello World: 1"
[INFO] [minimal_publisher]: Publishing: "Hello World: 2"
[INFO] [minimal_publisher]: Publishing: "Hello World: 3"
[INFO] [minimal_publisher]: Publishing: "Hello World: 4"

ros2 run cpp_pubsub listener

[INFO] [minimal_subscriber]: I heard: "Hello World: 10"
[INFO] [minimal_subscriber]: I heard: "Hello World: 11"
[INFO] [minimal_subscriber]: I heard: "Hello World: 12"
[INFO] [minimal_subscriber]: I heard: "Hello World: 13"
[INFO] [minimal_subscriber]: I heard: "Hello World: 14"

在每个终端中输入Ctrl+C以停止节点。