ROS2与C++入门教程-增加命名空间

ROS2与C++入门教程-增加命名空间

说明 ：

• 介绍如何增加命名空间

步骤：

• 新建一个包cpp_namespace

cd ~/dev_ws/src
ros2 pkg create --build-type ament_cmake cpp_namespace

• 进入include，新建头文件minimal_publisher_namespace.hpp

cd ~/dev_ws/src/cpp_namespace/include/cpp_namespace
touch minimal_publisher_namespace.hpp

• 内容如下：

#ifndef PUBLISHER_NAMESPACE_H_
#define PUBLISHER_NAMESPACE_H_

#include <chrono>
#include <functional>
#include <memory>
#include <string>

#include "rclcpp/rclcpp.hpp"
#include "std_msgs/msg/string.hpp"

using namespace std::chrono_literals;

namespace minimal
{

class MinimalPublisher : public rclcpp::Node
{
public:
  MinimalPublisher();

  private:
  void timer_callback();
  rclcpp::TimerBase::SharedPtr timer_;
  rclcpp::Publisher<std_msgs::msg::String>::SharedPtr publisher_;
  size_t count_;
};

} //namespace minimal
#endif /* PUBLISHER_NAMESPACE_H_ */

• 进入src目录，新建文件minimal_publisher_namespace.cpp

cd ~/dev_ws/src/cpp_namespace/src
touch minimal_publisher_namespace.cpp

• 内容如下：

#include "cpp_namespace/minimal_publisher_namespace.hpp"

namespace minimal
{
  
MinimalPublisher::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));
}

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

} //namespace minimal

• 进入src目录，新建文件minimal_publisher_namespace_node.cpp

cd ~/dev_ws/src/cpp_namespace/src
touch minimal_publisher_namespace_node.cpp

• 内容如下：

#include "cpp_namespace/minimal_publisher_namespace.hpp"
    
int main(int argc, char * argv[])
{
  rclcpp::init(argc, argv);
  rclcpp::spin(std::make_shared<minimal::MinimalPublisher>());
  rclcpp::shutdown();
  return 0;
}

• 编辑package.xml
• 在<buildtool_depend>ament_cmake</buildtool_depend>后增加

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

• 编辑 CMakelist.txt
• 在find_package(ament_cmake REQUIRED)后增加

find_package(rclcpp REQUIRED)
find_package(std_msgs REQUIRED)

• 再增加可执行文件，ros2 run能够调用的名称

include_directories(include)
add_executable(talker_namespace src/minimal_publisher_namespace_node.cpp src/minimal_publisher_namespace.cpp) 
ament_target_dependencies(talker_namespace rclcpp std_msgs)

• 增加可执行文件位置，ros2 run可以找到这个可执行文件

install(TARGETS
  talker_namespace
  DESTINATION lib/${PROJECT_NAME})

• 安装相关依赖

cd ~/dev_ws/
rosdep install -i --from-path src --rosdistro galactic -y

• 编译包

colcon build --symlink-install --packages-select cpp_namespace

• 加载工作空间

. install/setup.bash

• 执行

ros2 run cpp_namespace talker_namespace 

• 效果如下：

$ ros2 run cpp_namespace talker_namespace 
[INFO] [1651806323.835469215] [minimal_publisher]: NameSpace Publishing : 'Hello, world! NameSpace0'
[INFO] [1651806324.335468986] [minimal_publisher]: NameSpace Publishing : 'Hello, world! NameSpace1'
[INFO] [1651806324.835470570] [minimal_publisher]: NameSpace Publishing : 'Hello, world! NameSpace2'
[INFO] [1651806325.335460061] [minimal_publisher]: NameSpace Publishing : 'Hello, world! NameSpace3'
[INFO] [1651806325.835478477] [minimal_publisher]: NameSpace Publishing : 'Hello, world! NameSpace4'
[INFO] [1651806326.335481898] [minimal_publisher]: NameSpace Publishing : 'Hello, world! NameSpace5'
[INFO] [1651806326.835490994] [minimal_publisher]: NameSpace Publishing : 'Hello, world! NameSpace6'