rest - 如何从Github API获取JSON？

Question

我只想从以下网址获取JSON。
所以我用了这段代码:

extern crate reqwest;

fn main() -> Result<(), Box<dyn std::error::Error>> {
    let res = reqwest::Client::new()
        .get("https://api.github.com/users/octocat")
        .send()?
        .text()?;
    println!("{}", res);

    Ok(())
}

但我不知道如何解决该错误:

error[E0277]: the `?` operator can only be applied to values that implement `std::ops::Try`
  --> src\main.rs:19:15
   |
19 |       let res = reqwest::Client::new()
   |  _______________^
20 | |         .get("https://api.github.com/users/octocat")
21 | |         .send()?
   | |________________^ the `?` operator cannot be applied to type `impl std::future::Future`
   |
   = help: the trait `std::ops::Try` is not implemented for `impl std::future::Future`
   = note: required by `std::ops::Try::into_result`

error: aborting due to previous error

For more information about this error, try `rustc --explain E0277`.
error: could not compile `Desktop`.

但我也可以通过简单的方式获得想要的东西

curl https://api.github.com/users/octocat

我尝试添加 use std::ops::Try;，但效果不佳。

Answer 1

默认情况下，reqwest crate 可提供异步api。因此，在使用.await运算符处理错误之前，您必须先使用?。您还必须使用异步运行时，例如tokio:

#[tokio::main]
async fn main() -> Result<(), Box<dyn std::error::Error>> {
  let resp = reqwest::Client::new()
    .get("https://api.github.com/users/octocat")
    .send()
    .await?
    .json::<std::collections::HashMap<String, String>>()
    .await?;
  println!("{:#?}", resp);
  Ok(())
}

请注意，如上所示，要使用将响应转换为json，必须在 json中启用 Cargo.toml功能:

reqwest = { version = "0.10.8", features = ["json"] }

如果您不想使用异步运行时，则可以启用阻塞的 reqwest客户端:

[dependencies]
reqwest = { version = "0.10", features = ["blocking", "json"] }

并像这样使用它:

fn main() -> Result<(), Box<dyn std::error::Error>> {
  let resp = reqwest::blocking::Client::new()
    .get("https://api.github.com/users/octocat")
    .send()?
    .json::<std::collections::HashMap<String, String>>()?;
  println!("{:#?}", resp);
  Ok(())
}

Github的api需要其他几个配置选项。这是reqwest和github api的最小工作示例:

use reqwest::header::{HeaderMap, HeaderValue, USER_AGENT};
use serde::{Deserialize};

fn main() -> Result<(), Box<dyn std::error::Error>> {
  let mut headers = HeaderMap::new();
  // add the user-agent header required by github
  headers.insert(USER_AGENT, HeaderValue::from_static("reqwest"));

  let resp = reqwest::blocking::Client::new()
    .get("https://api.github.com/users/octocat")
    .headers(headers)
    .send()?
    .json::<GithubUser>()?;
  println!("{:#?}", resp);
  Ok(())
}

// Note that there are many other fields
// that are not included for this example
#[derive(Deserialize, Debug)]
pub struct GithubUser {
  login: String,
  id: usize,
  url: String,
  r#type: String,
  name: String,
  followers: usize
}