【ROS2】publisher和subscriber和延时编写规则

1、publisher

节点名 auto node = rclcpp::Node::make_shared(“publisher”);
消息类型和话题 auto pub = node->create_publisher(“/pub_sub”, 10);
发送消息 pub->publish(myMessage); //注意用->

#include "rclcpp/rclcpp.hpp"
#include "std_msgs/msg/string.hpp"
 
using namespace std::chrono_literals;
 
int main(int argc, char * argv[])
{
	  rclcpp::init(argc, argv);
	  auto node = rclcpp::Node::make_shared("publisher");
	  auto pub = node->create_publisher<std_msgs::msg::String>("/pub_sub", 10);
	 
	  std_msgs::msg::String myMessage;
	  size_t counter{0};
	  rclcpp::WallRate loop_rate(500ms);
	 
	  while (rclcpp::ok())
	  {
		    myMessage.data = "Hello, ros2 world! " + std::to_string(counter++);
		    RCLCPP_INFO(node->get_logger(), "Publishing: '%s'", myMessage.data.c_str());
		    try
		    {
			      pub->publish(myMessage);
			      rclcpp::spin_some(node);
		    } catch (const rclcpp::exceptions::RCLError & e)
		    {
		      	RCLCPP_ERROR(node->get_logger(), "Errore type : %s", e.what());
		    }
		    loop_rate.sleep();
	  }
	  rclcpp::shutdown();
	  return 0;
}

2、subscriber

节点名 node = std::make_sharedrclcpp::Node(“subscriber”);
消息类型和话题 auto sub = node->create_subscription(“/pub_sub”, 10, TopicCallback);
回调函数 void TopicCallback(const std_msgs::msg::String::SharedPtr msg) //注意用::SharedPtr
回调函数消息 msg->data //注意用->

#include "rclcpp/rclcpp.hpp"
#include "std_msgs/msg/string.hpp"
 
std::shared_ptr<rclcpp::Node> node = nullptr;
 
void TopicCallback(const std_msgs::msg::String::SharedPtr msg)
{
 	 RCLCPP_INFO(node->get_logger(), "I heard the message : '%s'", msg->data.c_str());
}
 
int main(int argc, char *argv[])
{
	  rclcpp::init(argc, argv);
	  node = std::make_shared<rclcpp::Node>("subscriber");
	  auto sub = node->create_subscription<std_msgs::msg::String>("/pub_sub", 10, TopicCallback);
	  rclcpp::spin(node);
	  rclcpp::shutdown();
	  return 0;
}

3、rqt_graph

4、延时sleep

  rclcpp::WallRate loop_rate(500ms);	//1s=1000ms,1ms=1000um,1um=1000nm
    while (rclcpp::ok())
  {
		......
	    loop_rate.sleep();
  }