rust - 如何编写返回 json 或 html 的简单 warp 处理程序？

Question

我有以下内容：

use warp::Filter;

pub struct Router {}

impl Router {
    pub async fn handle(
        &self,
    ) -> std::result::Result<impl warp::Reply, warp::Rejection> {

        let uri = "/path";

        match uri {
            "/metrics-list" => {
                let empty : Vec<u8> = Vec::new();
                Ok(warp::reply::json(&empty))
            }

            "/metrics-ips" => {
                let empty : Vec<u8> = Vec::new();
                Ok(warp::reply::json(&empty))
            }

            &_ => {
                Err(warp::reject::reject())
            }
        }
    }
}

#[tokio::main]
pub async fn main() {
    let r = Router {};

    let handler = warp::path("/").map(|| r.handle());

    warp::serve(handler);
    // .run(([0, 0, 0, 0], 3000))
    // .await;
}

但即使有这个简化的例子，我也会得到一个错误：

error[E0277]: the trait bound `impl warp::Future: warp::Reply` is not satisfied
  --> src/main.rs:41:17
   |
41 |     warp::serve(handler);
   |                 ^^^^^^^ the trait `warp::Reply` is not implemented for `impl warp::Future`
   |
  ::: $HOME/.cargo/registry/src/github.com-1ecc6299db9ec823/warp-0.2.5/src/server.rs:26:17
   |
26 |     F::Extract: Reply,
   |                 ----- required by this bound in `warp::serve`
   |
   = note: required because of the requirements on the impl of `warp::Reply` for `(impl warp::Future,)`

这是为什么？

标签： rustrust-tokiorust-warp

Answer 1

一种解决方案是调用.into_response()所有回复，然后将返回类型从更改std::result::Result<impl warp::Reply, warp::Rejection>为std::result::Result<warp::reply::Response, warp::Rejection>

pub async fn handle(
        &self,
    ) -> std::result::Result<warp::reply::Response, warp::Rejection> {

        let uri = "/path";

        match uri {
            "/metrics-list" => {
                let empty : Vec<u8> = Vec::new();
                Ok(warp::reply::json(&empty).into_response())
            }

            "/metrics-ips" => {
                let empty : Vec<u8> = Vec::new();
                Ok(warp::reply::json(&empty).into_response())
            }

            &_ => {
                Err(warp::reject::reject().into_response())
            }
        }
    }

原因是如果我正确理解这一点，那么impl Trait在您的返回类型中包含一个允许您一次只使用一种实现该特征的类型，因为您的函数只能有一种返回类型。