Is this the correct way to set up an asynchronous callback?

[mcitem]

This minimal example essentially expresses my needs.
I don't quite understand why we need to clone Weak again in app_login_.on_login(...).
I can't find more minimal examples (like those in the tokio/axum repository). How should I optimize my backend code?

[dependencies]
slint = "1.8.0"
async-compat = "0.2.4"
tokio = { version = "1.42.0", features = ["full"] }

slint::slint! {
import { LineEdit, Button } from "std-widgets.slint";
export component AppMain inherits Window {
    in property <string> username;
    width: 100px;
    height: 100px;
    Text {
        text: "Hello, " + username + "!";
    }
}

export component AppLogin inherits Window {
    property <string> user_id <=> l.text;
    in property <bool> enabled <=> b.enabled;
    callback login(string);
    VerticalLayout {
        padding: 10px;
        spacing: 10px;
        l := LineEdit { }

        b := Button {
            text: "Login";
            clicked => {
                login(user_id);
            }
        }
    }
}
}
use tokio::time::{sleep, Duration};

fn main() {
    let app_login = AppLogin::new().unwrap();
    let app_main = AppMain::new().unwrap();

    let main_weak = app_main.as_weak();
    let login_weak = app_login.as_weak();

    app_login.on_login(move |user_id| {
        // clone ?
        let main_weak_1 = main_weak.clone();
        let login_weak_1 = login_weak.clone();

        login_weak.upgrade().unwrap().set_enabled(false);

        let f = async move {
            if let Some(username) = login_req(&user_id).await {
                let main_w = main_weak_1.upgrade().unwrap();
                main_w.set_username(username.into());
                main_w.show().unwrap();

                login_weak_1.upgrade().unwrap().hide().unwrap();
            } else {
                login_weak_1.upgrade().unwrap().set_enabled(true);
            }
        };
        slint::spawn_local(async_compat::Compat::new(f)).unwrap();
    });
    app_login.run().unwrap();
}

async fn login_req(user_id: &str) -> Option<String> {
    println!("{} try Logging in...", user_id);
    sleep(Duration::from_secs(2)).await;
    match user_id {
        "root" => Some("Administrator".into()),
        _ => None,
    }
}

[ogoffart]

Yes, this is correct. you indeed need to clone the weak. There is no way around it, it is unfortunate that Rust is so verbose with clone.