Code shared from the Rust Playground

playground.rs

// error[E0277]: the trait bound `(): actix_web::ResponseError` is not satisfied
//  --> src/main.rs:25:32
//   |
//25 |             r.method(http::Method::GET).with_async(index)
//   |                                         ^^^^^^^^^^ the trait `actix_web::ResponseError` is not implemented for `()`
//   |
//   = note: required because of the requirements on the impl of `std::convert::From<()>` for `actix_web::Error`
//   = note: required because of the requirements on the impl of `std::convert::Into<actix_web::Error>` for `()`


extern crate hyper;
use std::io::{self, Write};
use hyper::{Client, Method, Request};
use hyper::rt::{self, Future, Stream};

extern crate serde;
extern crate serde_json;
#[macro_use]
extern crate serde_derive;
use serde_json::{Value};

extern crate actix_web;
use actix_web::{http, server, App, Path, Responder};

fn index(info: Path<(u32, String)>) -> impl Future<Item = String, Error = ()> {
    let client = Client::new();
    let url = "http://some.json.url".parse().unwrap();
    fetch_url(url)
}

fn main() {
    server::new(
        || App::new()
		.resource("/{id}/{name}/index.html", |r| {
			r.method(http::Method::GET).with_async(index)
		})
	).bind("127.0.0.1:8080").unwrap().run()
}


fn fetch_url(url: hyper::Uri) -> impl Future<Item = String, Error = ()> {
    let client = Client::new();

    client
        // Fetch the url...
        .get(url)
        // And then, if we get a response back...
        .and_then(|res| {
			res.into_body().concat2()
        })
        // If all good, just tell the user...
        .map(move |buffer| {
			let parsed = serde_json::from_slice::<Value>(&buffer).unwrap();
			println!("Done. {:#?}", parsed[0]["TRAIN_ID"]);
			format!("done: {:#?}", parsed[0]["TRAIN_ID"])
        })
        // If there was an error, let the user know...
        .map_err(|err| {
            eprintln!("Error {}", err);
        })
}