How to conditionally add routes to Axum Router?

Question

I'm using axum and this code to create a server but I get an error:

use axum::{response::Html, routing::get, Router};

async fn handler() -> Html<&'static str> {
    Html("<h1>Hello, World!</h1>")
}

#[tokio::main]
async fn main() {
    let router = Router::new();

    router.route("/", get(handler));

    if true { // I need to check something here
        router.route("/other", get(handler));
    }

    axum::Server::bind(&([127, 0, 0, 1], 3000).into())
        .serve(router.into_make_service())
        .await
        .unwrap();
}

error[E0382]: use of moved value: `router`
  --> src\main.rs:18:16
   |
9  |     let router = Router::new();
   |         ------ move occurs because `router` has type `Router`, which does not implement the `Copy` trait
10 |
11 |     router.route("/", get(handler));
   |     ------ value moved here
...
14 |         router.route("/other", get(handler));
   |         ------ value moved here
...
18 |         .serve(router.into_make_service())
   |                ^^^^^^ value used here after move

I tried with &router but I still get the error. How can I fix this? Should I use .clone()?

Because `.route` takes ownership of `router`. Documentation https://docs.rs/axum/latest/axum/struct.Router.html#method.route — Đorđe Zeljić, May 07 '22 at 22:09

score 4 · Answer 1 · answered May 07 '22 at 22:18

4

Using this code it works:

let mut router = Router::new();
router = router.route("/", get(handler));

if true {
    router = router.route(...);
}

answered May 07 '22 at 22:18

Fred Hors

3,258
3
25
71

score 1 · Accepted Answer · answered May 07 '22 at 22:21

Here is simplified code (Axum does the same thing). route takes ownership but also returns it.

#[derive(Debug)]
struct Router {
    list: Vec<String>,
}

impl Router {
    fn new() -> Self {
        Router { list: vec![] }
    }

    fn route(mut self, path: String) -> Self {
        self.list.push(path);
        self
    }
}

fn main() {
    let mut router = Router::new().route("/1".to_owned()).route("/2".to_owned());

    if true {
        router = router.route("/3".to_owned());
    }

    println!("{:?}", router);
}

So you have to set router in-line, or make it mut and reassign result of route to router variable.

How to conditionally add routes to Axum Router?

2 Answers2