Pub sub example

.rustfmt.toml

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+imports_granularity = "Crate"
+

your_package_name/Cargo.toml

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+[package]
+name = "your_package_name"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+[[bin]]
+name="simple_publisher"
+path="src/simple_publisher.rs"
+[[bin]]
+name="simple_subscriber"
+path="src/simple_subscriber.rs"
+[dependencies]
+rclrs = "*"
+std_msgs = "*"

your_package_name/package.xml

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+<package format="3">
+  <name>your_project_name</name>
+  <version>0.0.0</version>
+  <description>TODO: Package description. Seriously. Please make a Package description. We all will thank for it.</description>
+  <maintainer email="[email protected]">user</maintainer>
+  <license>TODO: License declaration. Licenses are Great. Please add a Licence</license>
+
+  <depend>rclrs</depend>
+  <depend>std_msgs</depend>
+
+  <export>
+    <build_type>ament_cargo</build_type>
+  </export>
+</package>

your_package_name/src/simple_publisher.rs

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+use rclrs::{create_node, Context, Node, Publisher, RclrsError, QOS_PROFILE_DEFAULT};
+/// Creates a SimplePublisherNode, initializes a node and publisher, and provides
+/// methods to publish a simple "Hello World" message on a loop in separate threads.
+
+/// Imports the Arc type from std::sync, used for thread-safe reference counting pointers,
+/// and the StringMsg message type from std_msgs for publishing string messages.
+use std::{sync::Arc, thread, time::Duration};
+use std_msgs::msg::String as StringMsg;
+// / SimplePublisherNode struct contains node and publisher members.
+// / Used to initialize a ROS 2 node and publisher, and publish messages.
+struct SimplePublisherNode {
+    node: Arc<Node>,
+    _publisher: Arc<Publisher<StringMsg>>,
+}
+/// The `new` function takes a context and returns a Result containing the
+/// initialized SimplePublisherNode or an error. It creates a node with the
+/// given name and creates a publisher on the "publish_hello" topic.
+///
+/// The SimplePublisherNode contains the node and publisher members.
+impl SimplePublisherNode {
+    /// Creates a new SimplePublisherNode by initializing a node and publisher.
+    ///
+    /// This function takes a context and returns a Result containing the
+    /// initialized SimplePublisherNode or an error. It creates a node with the
+    /// given name and creates a publisher on the "publish_hello" topic.
+    ///
+    /// The SimplePublisherNode contains the node and publisher members.
+    fn new(context: &Context) -> Result<Self, RclrsError> {
+        let node = create_node(context, "simple_publisher").unwrap();
+        let _publisher = node
+            .create_publisher("publish_hello", QOS_PROFILE_DEFAULT)
+            .unwrap();
+        Ok(Self { node, _publisher })
+    }
+
+    /// Publishes a "Hello World" message on the publisher.
+    ///
+    /// Creates a StringMsg with "Hello World" as the data, publishes it on
+    /// the `_publisher`, and returns a Result. This allows regularly publishing
+    /// a simple message on a loop.
+    fn publish_data(&self, increment: i32) -> Result<i32, RclrsError> {
+        let msg: StringMsg = StringMsg {
+            data: format!("Hello World {}", increment),
+        };
+        self._publisher.publish(msg).unwrap();
+        Ok(increment + 1_i32)
+    }
+}
+
+/// The main function initializes a ROS 2 context, node and publisher,
+/// spawns a thread to publish messages repeatedly, and spins the node
+/// to receive callbacks.
+///
+/// It creates a context, initializes a SimplePublisherNode which creates
+/// a node and publisher, clones the publisher to pass to the thread,  
+/// spawns a thread to publish "Hello World" messages repeatedly, and
+/// calls spin() on the node to receive callbacks. This allows publishing
+/// messages asynchronously while spinning the node.
+fn main() -> Result<(), RclrsError> {
+    let context = Context::new(std::env::args()).unwrap();
+    let publisher = Arc::new(SimplePublisherNode::new(&context).unwrap());
+    let publisher_other_thread = Arc::clone(&publisher);
+    let mut count: i32 = 0;
+    thread::spawn(move || loop {
+        thread::sleep(Duration::from_millis(1000));
+        count = publisher_other_thread.publish_data(count).unwrap();
+    });
+    rclrs::spin(publisher.node.clone())
+}

your_package_name/src/simple_subscriber.rs

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+use rclrs::{create_node, Context, Node, RclrsError, Subscription, QOS_PROFILE_DEFAULT};
+use std::{
+    env,
+    sync::{Arc, Mutex},
+    thread,
+    time::Duration,
+};
+use std_msgs::msg::String as StringMsg;
+/// A simple ROS2 subscriber node that receives and prints "hello" messages.
+///
+/// This node creates a subscription to the "publish_hello" topic and prints the
+/// received messages to the console. It runs the subscription in a separate
+/// thread, while the main thread calls `rclrs::spin()` to keep the node running.
+pub struct SimpleSubscriptionNode {
+    node: Arc<Node>,
+    _subscriber: Arc<Subscription<StringMsg>>,
+    data: Arc<Mutex<Option<StringMsg>>>,
+}
+/// Implements a simple ROS2 subscriber node that receives and prints "hello" messages.
+/// The `new` function creates the node and the subscription, and returns a `SimpleSubscriptionNode`
+/// instance. The `data_callback` function can be used to access the latest received message.
+impl SimpleSubscriptionNode {
+    fn new(context: &Context) -> Result<Self, RclrsError> {
+        let node = create_node(context, "simple_subscription").unwrap();
+        let data: Arc<Mutex<Option<StringMsg>>> = Arc::new(Mutex::new(None));
+        let data_mut: Arc<Mutex<Option<StringMsg>>> = Arc::clone(&data);
+        let _subscriber = node
+            .create_subscription::<StringMsg, _>(
+                "publish_hello",
+                QOS_PROFILE_DEFAULT,
+                move |msg: StringMsg| {
+                    *data_mut.lock().unwrap() = Some(msg);
+                },
+            )
+            .unwrap();
+        Ok(Self {
+            node,
+            _subscriber,
+            data,
+        })
+    }
+    fn data_callback(&self) -> Result<(), RclrsError> {
+        if let Some(data) = self.data.lock().unwrap().as_ref() {
+            println!("{}", data.data);
+        } else {
+            println!("No message available yet.");
+        }
+        Ok(())
+    }
+}
+/// The `main` function creates a new ROS2 context, a `SimpleSubscriptionNode` instance, and starts a separate thread to periodically call the `data_callback` method on the subscription. The main thread then calls `rclrs::spin()` to keep the node running and receive messages.
+///
+/// The separate thread is used to ensure that the `data_callback` method is called regularly, even if the main thread is blocked in `rclrs::spin()`. This allows the subscriber to continuously process and print the received "hello" messages.
+fn main() -> Result<(), RclrsError> {
+    let context = Context::new(env::args()).unwrap();
+    let subscription = Arc::new(SimpleSubscriptionNode::new(&context).unwrap());
+    let subscription_other_thread = Arc::clone(&subscription);
+    thread::spawn(move || loop {
+        thread::sleep(Duration::from_millis(1000));
+        subscription_other_thread.data_callback().unwrap()
+    });
+    rclrs::spin(subscription.node.clone())
+}