Should handlers be functions only?

[marioidival]

I'm tying do a sort of handlers in an struct, how I can this with actix-web?

Ex:

struct A;
impl A {
   async fn foo // omit
}

let a = A();
.route("/foo", web::get().to(a.foo)

[aliemjay]

You want the handler to store the data of a. This is possible by defining a closure that captures a:

.to(|| async move { a.foo().await }) 

[marioidival]

Sorry about that, @aliemjay , I do not use async because I had a problem with the Responder but my correct example:

pub struct Controller;
impl Controller {
  pub fn handler(&self) -> impl Responder {
    HttpResponse::Ok().body("some response")
  }
}

// omit
let c = Controller;
// omit
.route("/foo", web::cet().to(c.handler)

This not working.

[marioidival]

You want the handler to store the data of a. This is possible by defining a closure that captures a:

.to(|| async move { a.foo().await }) 

This example throw an error
error[E0525]: expected a closure that implements the `Fn` trait, but this closure only implements `FnOnce` --> src/main.rs:152:48 | 152 | ... web::post().to(|| async move { my_controller.handler().await }), | -- ^^^^^^^^^^^^^ --------------------------------- closure is `FnOnce` because it moves the variable `my_controller` out of its environment | | | | | this closure implements `FnOnce`, not `Fn` | the requirement to implement `Fn` derives from here

[aliemjay]

Sorry, I made a mistake. This should work for async:

.to(move || a.foo())

For non-async:

.to(move || {
    let response = a.foo();
    async { response }
})

[aliemjay]

Please see my updated response. There is no problem with your implementation. I should've tested it locally before suggesting it :)

[marioidival]

It works!

[marioidival]

Now, my problem is how I can pass the HttpRequest into it 🗡️

[aliemjay]

This would be

.to(move |req| {
    let response = controller.handler(req);
    async { response }
})

[aliemjay]

It works but it may be tricky and not user-friendly solution and you may face more problems with it.

I recommend that you have all your handlers as async functions and you can then access controller in them by passing it to App::app_data. You can see the docs for app state in https://actix.rs/docs/application/

[robjtede]

See that the handler trait includes a 'static bound.
https://github.com/actix/actix-web/blob/master/src/handler.rs#L22

In effect, it is pretty difficult to use struct methods as handlers in a useful way since you need to move the struct into the closure to use it. This is why all the teaching materials use functions; the framework is designed around it. So yes, handlers should be functions/closures.