【ROS2】ROS2 与 ROS1 编码方式对比（C++实现）

不仅客户端库有不同，ROS2 在代码编写方式上相对于ROS1也有了一些重要的变化，包括一些核心概念和实践方法的调整。ROS1代码编写方式更倾向于过程式思想，ROS2则使用了更多的面向对象的方式，也添加了更多的现代编程思想的使用。

ROS2 在 C++ 编程中引入了一些新的概念和 API，这些变化使得代码更加模块化和易于维护。特别是 rclcpp 库提供了更丰富的功能和更好的错误处理机制，同时支持异步编程模型。如果你已经熟悉 ROS1 的 C++ 编程，这些变化应该不会太难适应。主要的区别在于初始化、节点管理、服务和客户端的创建和调用方式。

一、初始化和关闭节点

ROS1:

#include "ros/ros.h"int main(int argc, char **argv) 
{ros::init(argc, argv, "my_node");ros::NodeHandle nh;// 节点逻辑ros::spin();return 0;
}

ROS2:

#include "rclcpp/rclcpp.hpp"int main(int argc, char **argv) 
{rclcpp::init(argc, argv);auto node = rclcpp::Node::make_shared("my_node");// 节点逻辑rclcpp::spin(node);rclcpp::shutdown();return 0;
}

二、发布者和订阅者

ROS1:

// 发布者
ros::Publisher pub = nh.advertise<std_msgs::String>("chatter", 10);// 订阅者
ros::Subscriber sub = nh.subscribe("chatter", 10, chatterCallback);
void chatterCallback(const std_msgs::String::ConstPtr& msg) 
{ROS_INFO("I heard: [%s]", msg->data.c_str());
}

ROS2:

// 发布者
auto pub = node->create_publisher<std_msgs::msg::String>("chatter", 10);// lambda函数版订阅者
auto sub = node->create_subscription<std_msgs::msg::String>("chatter", 10, [](const std_msgs::msg::String::SharedPtr msg){RCLCPP_INFO(rclcpp::get_logger("my_node"), "I heard: '%s'", msg->data.c_str());}
);// 成员函数版订阅者
rclcpp::Subscription<std_msgs::msg::String>::SharedPtr subscription_;
subscription_ = this->create_subscription<std_msgs::msg::String>("topic", 10, std::bind(&MinimalSubscriber::topic_callback, this, _1));
void topic_callback(const std_msgs::msg::String &msg) const
{RCLCPP_INFO(this->get_logger(), "I heard: '%s'", msg.data.c_str());
}

三、服务和客户端

ROS1:

// 服务
ros::ServiceServer service = nh.advertiseService("add_two_ints", add_two_ints_callback);
bool add_two_ints_callback(srv::AddTwoInts::Request &req, srv::AddTwoInts::Response &res) 
{res.sum = req.a + req.b;ROS_INFO("request: x=%ld, y=%ld", (long int)req.a, (long int)req.b);ROS_INFO("sending back response: [%ld]", (long int)res.sum);return true;
}// 客户端
client = nh.serviceClient<srv::AddTwoInts>("add_two_ints");
srv::AddTwoInts srv;
srv.request.a = 1;
srv.request.b = 2;
if (client.call(srv)) 
{ROS_INFO("Sum: %ld", (long int)srv.response.sum);
} 
else 
{ROS_ERROR("Failed to call service add_two_ints");
}

ROS2:

// 服务
auto service = node->create_service<example_interfaces::srv::AddTwoInts>("add_two_ints", add);
void add(const std::shared_ptr<example_interfaces::srv::AddTwoInts::Request> request, std::shared_ptr<example_interfaces::srv::AddTwoInts::Response> response) 
{response->sum = request->a + request->b;RCLCPP_INFO(node->get_logger(), "request: x=%ld, y=%ld", request->a, request->b);RCLCPP_INFO(node->get_logger(), "sending back response: [%ld]", response->sum);
}// 客户端
auto client = node->create_client<example_interfaces::srv::AddTwoInts>("add_two_ints");auto request = std::make_shared<example_interfaces::srv::AddTwoInts::Request>();
request->a = 1;
request->b = 2;auto future = client->async_send_request(request);
if (rclcpp::spin_until_future_complete(node, future) == rclcpp::FutureReturnCode::SUCCESS) 
{RCLCPP_INFO(node->get_logger(), "Sum: %ld", future.get()->sum);
} 
else 
{RCLCPP_ERROR(node->get_logger(), "Failed to call service add_two_ints");
}

四、参数管理

ROS1:

std::string param_value;
nh.getParam("param_name", param_value);

ROS2:

auto param_value = node->get_parameter("param_name").as_string();

五、日志记录

ROS1:

ROS_INFO("This is an info message.");
ROS_DEBUG("This is a DEBUG message");
ROS_INFO("This is an INFO message");
ROS_WARN("This is a WARN message");
ROS_ERROR("This is an ERROR message");
ROS_FATAL("This is a FATAL message");

ROS2:

RCLCPP_INFO(this->get_logger(), "This is an info message.");
RCLCPP_DEBUG(this->get_logger(), "This is a DEBUG message");
RCLCPP_INFO(this->get_logger(), "This is an INFO message");
RCLCPP_WARN(this->get_logger(), "This is a WARN message");
RCLCPP_ERROR(this->get_logger(), "This is an ERROR message");
RCLCPP_FATAL(this->get_logger(), "This is a FATAL message");

六、生命周期管理

ROS1:

ROS1 没有内置的生命周期管理功能，通常需要开发者自己实现节点的生命周期管理。

ROS2:

ROS2 引入了生命周期节点的概念，允许更精细地控制节点的启动和停止过程。

class LifecycleNode : public rclcpp_lifecycle::LifecycleNode 
{
public:LifecycleNode() : LifecycleNode("lifecycle_node") {}LifecycleNode(std::string name) : rclcpp_lifecycle::LifecycleNode(name) {}rclcpp_lifecycle::node_interfaces::LifecycleNodeInterface::CallbackReturn on_configure(const rclcpp_lifecycle::State &state) override {RCLCPP_INFO(get_logger(), "on_configure() is called.");return rclcpp_lifecycle::node_interfaces::LifecycleNodeInterface::CallbackReturn::SUCCESS;}rclcpp_lifecycle::node_interfaces::LifecycleNodeInterface::CallbackReturn on_activate(const rclcpp_lifecycle::State &state) override {RCLCPP_INFO(get_logger(), "on_activate() is called.");return rclcpp_lifecycle::node_interfaces::LifecycleNodeInterface::CallbackReturn::SUCCESS;}// 其他生命周期回调函数...
};