Question

我遇到了编译错误，我不太了解Hyper的master分支中的示例略有修改。给出以下代码：

extern crate futures;
extern crate hyper;

use futures::future::FutureResult;
use hyper::header::{ContentLength, ContentType};
use hyper::server::{Http, Service, Request, Response, Server, NewService};
use hyper::Body;
use std::fmt::Display;
use std::result;

static PHRASE: &'static [u8] = b"Hello World!";

#[derive(Clone, Copy)]
pub struct MyService {}

impl Service for MyService {
    type Request = Request;
    type Response = Response;
    type Error = hyper::Error;
    type Future = FutureResult<Response, hyper::Error>;
    fn call(&self, _req: Request) -> Self::Future {
        return futures::future::ok(Response::new()
            .with_header(ContentLength(PHRASE.len() as u64))
            .with_header(ContentType::plaintext())
            .with_body(PHRASE));
    }
}

#[derive(Clone)]
pub struct MyServer {}

#[derive(Debug)]
pub struct MyServeError(String);
impl<T: Display> From<T> for MyServeError {
    fn from(e: T) -> MyServeError {
        return MyServeError(format!("{}", e));
    }
}

type Result<T> = result::Result<T, MyServeError>;


impl MyServer {
    pub fn new() -> MyServer {
        return MyServer {};
    }

    fn get_server(&self) -> Result<Server<&MyServer, Body>> {
        let addr = format!("127.0.0.1:8080").parse()?;
        return Ok(Http::new().bind(&addr, self)?);
    }
}

impl NewService for MyServer {
    type Request = Request;
    type Response = Response;
    type Instance = MyService;
    type Error = hyper::Error;

    fn new_service(&self) -> std::io::Result<Self::Instance> {
        let service = MyService {};
        Ok(service)
    }
}

我收到此编译错误：

 Compiling hyper-problem-demo v0.1.0 (file:///.../hyper-problem-demo)
error[E0277]: the trait bound `MyServer: std::ops::Fn<()>` is not satisfied
  --> src/lib.rs:50:31
   |
50 |         return Ok(Http::new().bind(&addr, self)?);
   |                               ^^^^ the trait `std::ops::Fn<()>` is not implemented for `MyServer`
   |
   = note: required because of the requirements on the impl of `std::ops::FnOnce<()>` for `&MyServer`
   = note: required because of the requirements on the impl of `hyper::server::NewService` for `&MyServer`

error[E0277]: the trait bound `MyServer: std::ops::FnOnce<()>` is not satisfied
  --> src/lib.rs:50:31
   |
50 |         return Ok(Http::new().bind(&addr, self)?);
   |                               ^^^^ the trait `std::ops::FnOnce<()>` is not implemented for `MyServer`
   |
   = note: required because of the requirements on the impl of `hyper::server::NewService` for `&MyServer`

我真的不明白。我的目的只是使用MyServer对象为超级创建MyService的新实例，因此实现NewService似乎有意义，但我不明白为什么会这样做要求实施Fn()。 NewService实际上是为Fn() -> io::Result<Service实施的，所以可能会以某种方式发生冲突？

有一个完整的示例项目here。

Answer 1

您已为NewService实施了MyServer，但是您提供的bind &MyServer无法找到NewService的实施内容。

您选择的解决方案在很大程度上取决于您为什么要这样做，但您可以为NewService实施&MyServer：

impl<'a> NewService for &'a MyServer {
    ...
}

Hyper的编译错误

1 个答案: