How to conditionally add routes to Axum Router? - rust

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()?

Answer 1

Using this code it works:
let mut router = Router::new();
router = router.route("/", get(handler));
if true {
router = router.route(...);
}

Answer 2

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.