This breaks up `extract.rs` into several smaller submodules. The public
API remains the same.
This is done in prep for adding more tests to extractors which would get
messy if they were all in the same file.
Fixes https://github.com/tokio-rs/axum/issues/43
With this you can get the remote address like so:
```rust
use axum::{prelude::*, extract::ConnectInfo};
use std::net::SocketAddr;
let app = route("/", get(handler));
async fn handler(ConnectInfo(addr): ConnectInfo<SocketAddr>) -> String {
format!("Hello {}", addr)
}
// Starting the app with `into_make_service_with_connect_info` is required
// for `ConnectInfo` to work.
let make_svc = app.into_make_service_with_connect_info::<SocketAddr, _>();
hyper::Server::bind(&"0.0.0.0:3000".parse().unwrap())
.serve(make_svc)
.await
.expect("server failed");
```
This API is fully generic and supports whatever transport layer you're using with Hyper. I've updated the unix domain socket example to extract `peer_creds` and `peer_addr`.
Previously extractors worked directly on `Request<B>` which meant you
had to do weird tricks like `mem::take(req.headers_mut())` to get owned
parts of the request.
This changes that instead to use a new `RequestParts` type that have
methods to "take" each part of the request. Without having to do weird
tricks.
Also removed the need to have `B: Default` for body extractors.
