Function actix_web_lab::middleware::from_fn

pub fn from_fn<F, Es>(mw_fn: F) -> MiddlewareFn<F, Es>

Wraps an async function to be used as a middleware.

Examples

The wrapped function should have the following form:

use actix_web_lab::middleware::Next;

async fn my_mw(
    req: ServiceRequest,
    next: Next<impl MessageBody>,
) -> Result<ServiceResponse<impl MessageBody>, Error> {
    // pre-processing
    next.call(req).await
    // post-processing
}

Then use in an app builder like this:

use actix_web::{
    App, Error,
    dev::{ServiceRequest, ServiceResponse, Service as _},
};
use actix_web_lab::middleware::from_fn;

App::new()
    .wrap(from_fn(my_mw))

It is also possible to write a middleware that automatically uses extractors, similar to request handlers, by declaring them as the first parameters:

use actix_web_lab::middleware::Next;

async fn my_extracting_mw(
    string_body: String,
    query: web::Query<HashMap<String, String>>,
    req: ServiceRequest,
    next: Next<impl MessageBody>,
) -> Result<ServiceResponse<impl MessageBody>, Error> {
    // pre-processing
    next.call(req).await
    // post-processing
}