ros2-docs/docs/General ROS 2/Building ROS 2 Packages/ROS 2 Subscriber.md

ROS 2 Subscriber

Sample Code

Here is the code for creating a python node that subscribes to /robot_news at 2Hz.

=== "Python" ``` python title="smartphone.py" linenums="1" #!/usr/bin/env python

import rclpy
from rclpy.node import Node
from example_interfaces.msg import String

class SmartphoneNode(Node):

	def __init__(self):
		super().__init__("smartphone")
		self.subscriber_ = self.create_subscription(String, 'robot_news', self.callback_robot_news, 10)
		self.get_logger().info("Smartphone has been starte.")
	
	def callback_robot_news(self, msg):
		self.get_logger().info(msg.data)

def main (args=None):
	rclpy.init(args=args)
	node = SmartphoneNode()
	rclpy.spin(node)
	rclpy.shutdown()


if __name__ == '__main__':
	main()
```

=== "C++" ``` python title="smartphone.cpp" linenums="1" #include "rclcpp/rclcpp.hpp" #include "example_interfaces/msg/string.hpp"

class SmartphoneNode : public rclcpp::Node
{
public:
	SmartphoneNode() : Node("smartphone")
	{
		subscriber_ = this->create_subscription<example_interfaces::msg::String>(
				"robot_news", 10,
				std::bind(&SmartphoneNode::callbackRobotNews, this, std::placeholders::_1));
		RCLCPP_INFO(this->get_logger(), "Smartphone has been started.");
	}

private:
	void callbackRobotNews(const example_interfaces::msg::String::SharedPtr msg)
	{
		RCLCPP_INFO(this->get_logger(), "%s", msg->data.c_str());
	}
	rclcpp::Subscription<example_interfaces::msg::String>::SharedPtr subscriber_;
};


int main(int argc, char **argv)
{
	rclcpp::init(argc, argv);
	auto node = std::make_shared<SmartphoneNode>();
	rclcpp::spin(node);
	rclcpp::shutdown();
	return 0;
}
```