Hello Goodbye

Hello World is a classic first project, but we also want to showcase how the runtime exits. To start, simply create a new project with any name you'd like:

cargo new hello-goodbye

Once you've done that, simply add the following to the dependencies in Cargo.toml:

unros = "0.1"

Now, we shall start coding exclusively in main.rs. First, let us modify the main method. Here is what a classic one would look like:

fn main() {
    println!("Hello world!");
}

The entire execution of the program is encapsulated within this method. In robotics, we typically have several systems that work concurrently and persistently. There is a lot of boilerplate involved in running these correctly, so we've handled that for you! Simply use the procedural macro, much in the same way as tokio::main:

use unros::{Application, anyhow};

#[unros::main]
async fn main(app: Application) -> anyhow::Result<Application> {
    println!("Hello world!");
    Ok(app)
}

We've added quite a few things:

#[unros::main]
Invokes a procedural macro to add the boilerplate code.

async fn main(app: Application) -> anyhow::Result<Application>
main can now run asynchronous code. The async runtime is generated automatically. The method now also accepts an Application object. Nodes and tasks are added to this Application which queues them up for execution. This Application object is then returned assuming no errors occurred. If an error did occur, you can safely return it for it to be displayed according to anyhow's formatting.

This Application object is key, as it means that the application itself does not run until the main method exits. Now, the entire execution of the program is no longer encapsulated in main, so what is main's purpose? Initialization. We always want errors to appear as early as possible, so perform all of your extensive error checking here before returning a correctly made Application object, and let Unros handle the rest.

So, what does the Application do right now? Well, nothing! It has not been modified at all, so Unros will not do anything. Try running the application right now.

cargo run

[0:0.00 unros_core] Runtime started with pid: 220566
Hello World!
[0:0.00 unros_core] All nodes have terminated
[0:0.00 unros_core] Exiting...

The program seems to be working just fine! You should also have noticed that a logs folder was generated, and there is a .log inside with the following contents:

[0:0.00 INFO unros_core] Runtime started with pid: 220566
[0:0.00 DEBUG auxilliary-control] Successfully binded to: 0.0.0.0:44537
[0:0.00 INFO unros_core] All nodes have terminated
[0:0.00 INFO unros_core] Exiting...

Note that Hello World! is not present. This is because the log file only stores actual logs and not stdout. This may be subject to change. Ignore the auxilliary-control line for now. Your pid will also be different. You can use this to kill the process if all else fails (which hopefully does not happen).