What's the return type of bind(..).serve(...)?

[luos]

Hi,

I am new to Rust, sorry for this beginner question. I am trying to find out what is the return type of the serve method so I can put it in a function. I tried some which look like they could work but they are from private modules.

Here is what I am trying to achieve:

I am trying to find the return type of the start_web_handler function, highlighted with ??.

async fn  start_web_handler() -> Server<??AddrIncoming??, ??IntoMakeService<Router>??> {
    let app = Router::new().route("/", get(|| async { "Hello, World!" }));

    // run it with hyper on localhost:3000
    let addr = SocketAddr::from(([127, 0, 0, 1], 3000));
    let s = axum::Server::bind(&addr)
        .serve(app.into_make_service());
    s
}

Thanks,

[davidpdrsn]

From looking at the docs we see that serve returns a Server which implements Future where the Output is hyper::Result<()>. So if you add a .await inside your function the return type becomes Result<(), hyper::Error>.

[luos]

I guess I got a little bit confused about putting await into this method, as I wanted to "propagate" the future out.
I got it working how I wanted now. Thank you!

pub async fn  start_listener() -> Result<(), hyper::Error> {
    let app = Router::new().route("/", get(|| async { "Hello, World!" }));

    // run it with hyper on localhost:3000
    let addr = SocketAddr::from(([127, 0, 0, 1], 3000));
    let s = axum::Server::bind(&addr)
        .serve(app.into_make_service());
    s.await
}

[davidpdrsn]

Right yeah that can be a little confusing. But it works since start_listener is itself an async fn. So nothing happens unless the caller awaits the future returned by start_listener.

[Daniel-Xu]

Is it idiomatic to return the Server in this case? ( i need to run it later in run_until_stop)

[davidpdrsn]

Sure. Why not? I mean the type is a bit big but otherwise I don't see any issues if it works.