无法读取通过hyper :: client :: Client发出HTTP请求的简单有效负载:不满足特征绑定`Body:Future` [英] Can't read a simple payload making HTTP request via hyper::client::Client: the trait bound `Body: Future` is not satisfied

问题描述

我正在尝试将结果转换为 Buffer :

let ufc_root: String =
    String::from("https://www.ufc.com/athletes/all?filters%5B0%5D=status%3A23");
// let ufc_root: String = String::from("https://www.google.com");
let https = HttpsConnector::new(4).unwrap();
let client = Client::builder().build::<_, hyper::Body>(https);

client
    .get(ufc_root.parse::<hyper::Uri>().unwrap())
    .and_then(|res| {
        println!("http status code: {}", res.status());
        println!("http response headers:\n{:?}: ", res.headers());
        res.into_body()
    })
    .from_err::<WebScrapeError>()
    .and_then(|body| {
        body.for_each(|chunk| {
            println!("{}", chunk.into_bytes());
        });

        let jon_jones = Subject {
            name: "Jon Jones".to_string(),
            link: "http://www.jonjones.com".to_string(),
        };
        let subjects = vec![jon_jones];
        Ok(subjects)
    })
    .from_err()

error[E0277]: the trait bound `hyper::Body: hyper::rt::Future` is not satisfied
  --> src/scrapper.rs:24:14
   |
24 |             .and_then(|res| {
   |              ^^^^^^^^ the trait `hyper::rt::Future` is not implemented for `hyper::Body`
   |
   = note: required because of the requirements on the impl of `futures::future::IntoFuture` for `hyper::Body`

error[E0599]: no method named `from_err` found for type `futures::future::and_then::AndThen<hyper::client::ResponseFuture, hyper::Body, [closure@src/scrapper.rs:24:23: 28:14]>` in the current scope
  --> src/scrapper.rs:29:14
   |
29 |             .from_err::<WebScrapeError>()
   |              ^^^^^^^^
   |
   = note: the method `from_err` exists but the following trait bounds were not satisfied:
           `&mut futures::future::and_then::AndThen<hyper::client::ResponseFuture, hyper::Body, [closure@src/scrapper.rs:24:23: 28:14]> : hyper::rt::Future`
           `&mut futures::future::and_then::AndThen<hyper::client::ResponseFuture, hyper::Body, [closure@src/scrapper.rs:24:23: 28:14]> : hyper::rt::Stream`
           `futures::future::and_then::AndThen<hyper::client::ResponseFuture, hyper::Body, [closure@src/scrapper.rs:24:23: 28:14]> : hyper::rt::Future`

为什么不编译?

推荐答案

and_then 必须返回将来，或者可以通过

and_then must return a future, or something that can be converted into a future via the IntoFuture trait. You're returning res.into_body(), which is not a future - it's actually a stream.

要使其正常工作，您需要将该流转换为将来的内容，以表示该主体已被完全读取.这里有几个可用的选项:

To get this to work, you'll need to convert that stream into a future which represents the body having been fully read. There's several options available to you here:

• res.into_body().concat2()，它将所有读取的字节连接到单个缓冲区中
• res.into_body().collect()，它将所有字节块收集到 Vec
• res.into_body().into_future()，它将解析为一个元组，其中包含流中的第一项以及流本身的其余部分(即(T，Stream< Item = T>))

• res.into_body().concat2(), which concatenates all of the read bytes into a single buffer
• res.into_body().collect(), which collects all of the chunks of bytes into a Vec
• res.into_body().into_future(), which will resolve to a tuple containing the first item from the stream, and the remainder of the stream itself (i.e. (T, Stream<Item = T>))

存在多种不同(同等有效)方式将 Stream 表示为 Future 的事实，这可能是为什么前者没有全面实现 IntoFuture .

The fact that there's multiple different (and equally valid) ways to represent a Stream as a Future is likely why the former doesn't have a blanket implementation of IntoFuture.

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