Better way to share value in middlelayer functions than using `middlelayer::from_fn_with_state`? #3212

HaoYang670 · 2025-02-05T07:10:18Z

HaoYang670
Feb 5, 2025

Summary

I am writing an auth layer for my app and I am currently putting the auth client into the State and use it by middlelayer::from_fn_with_state. I actually don't want it to be in State as it is only used in the authentication. Do you know if there is a way to move it out? (I've tried to use function closure in middlelayer::from_fn to capture the value, but it is not supported.)

axum version

0.8.1

Answered by HaoYang670

Feb 5, 2025

The state you pass to from_fn_with_state does not have to be the same state you use elsewhere.

This can work. Thanks!

View full answer

jplatte · 2025-02-05T07:35:57Z

jplatte
Feb 5, 2025
Maintainer

The state you pass to from_fn_with_state does not have to be the same state you use elsewhere.

Also, closure captures definitely work. Feel free to post the error you're getting and I can try to explain what's wrong.

3 replies

HaoYang670 Feb 5, 2025
Author

Thanks, @jplatte, for your quick response.

The state you pass to from_fn_with_state does not have to be the same state you use elsewhere.

Do you mean I can pass different states to from_fn_with_state and Router::with_state? I will take a try for it.

Also, closure captures definitely work. Feel free to post the error you're getting and I can try to explain what's wrong.

I am now putting the auth client in State and it works (https://github.com/HaoYang670/rucat/blob/c149f44923bb3498a544975c2aa95e4d7954245c/rucat_server/src/lib.rs#L55), but I got compile error:

error[E0525]: expected a closure that implements the `FnMut` trait, but this closure only implements `FnOnce`
   --> rucat_server/src/lib.rs:57:36
    |
57  |         .layer(middleware::from_fn(move |headers: HeaderMap, request: Request, next: Next| auth(auth_provider, headers, request, next)))
    |          ----- --------------------^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^---------------------------------------------
    |          |     |                   |                                                            |
    |          |     |                   |                                                            closure is `FnOnce` because it moves the variable `auth_provider` out of its environment
    |          |     |                   this closure implements `FnOnce`, not `FnMut`
    |          |     the requirement to implement `FnMut` derives from here
    |          required by a bound introduced by this call
    |
    = note: required for `FromFn<{closure@lib.rs:57:36}, (), Route, (HeaderMap, Request<Body>)>` to implement `tower_service::Service<http::Request<Body>>`
rustc[E0525](rust-analyzer-diagnostics-view:/diagnostic%20message%20%5B0%5D?0#file%3A%2F%2F%2FUsers%2Fremziy%2FFangcloudV2%2Fpersonal_space.localized%2Flearning%2Fcomputer_science%2Frucat%2Frucat_server%2Fsrc%2Flib.rs)
lib.rs(57, 16): the requirement to implement `FnMut` derives from here
lib.rs(57, 97): closure is `FnOnce` because it moves the variable `auth_provider` out of its environment
lib.rs(57, 10): required by a bound introduced by this call
mod.rs(300, 21): required by a bound in `Router::<S>::layer`

After changing to use closure. I put my source code here: https://github.com/HaoYang670/rucat/blob/3ef4a23f89a580d8fc28805e9ee69cd0a3d02de3/rucat_server/src/lib.rs#L57

HaoYang670 Feb 5, 2025
Author

The state you pass to from_fn_with_state does not have to be the same state you use elsewhere.

This can work. Thanks!

Answer selected by HaoYang670

mladedav Feb 5, 2025
Collaborator

Just for the error, try cloning the auth_provider insidde the closure. Then the closure could hopefully be called multiple times and be FnMut and not just FnOnce as the error is trying to tell you.

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Better way to share value in middlelayer functions than using middlelayer::from_fn_with_state? #3212

HaoYang670 Feb 5, 2025

Summary

axum version

Replies: 1 comment · 3 replies

jplatte Feb 5, 2025 Maintainer

HaoYang670 Feb 5, 2025 Author

HaoYang670 Feb 5, 2025 Author

mladedav Feb 5, 2025 Collaborator

Better way to share value in middlelayer functions than using `middlelayer::from_fn_with_state`? #3212

HaoYang670
Feb 5, 2025

Replies: 1 comment 3 replies

jplatte
Feb 5, 2025
Maintainer

HaoYang670 Feb 5, 2025
Author

HaoYang670 Feb 5, 2025
Author

mladedav Feb 5, 2025
Collaborator