Getting started

In order to build a web app in Rust you need an HTTP server, and an async runtime. After running cargo new --bin web-app add the following lines to your Cargo.toml file:

# Example, use the version numbers you need
tide = "0.15.0"
async-std = { version = "1.6.5", features = ["attributes"] }

Example

Create an HTTP server that receives a JSON body, validates it, and responds with a confirmation message.

use tide::prelude::*;
use tide::Request;

#[derive(Debug, Deserialize)]
struct Animal {
    name: String,
    legs: u8,
}

#[async_std::main]
async fn main() -> tide::Result<()> {
    tide::log::start();
    let mut app = tide::new();

    app.at("/orders/shoes").post(order_shoes);
    app.listen("127.0.0.1:8080").await?;

    Ok(())
}

async fn order_shoes(mut req: Request<()>) -> tide::Result {
    let Animal { name, legs } = req.body_json().await?;
    Ok(format!("Hello, {}! I've put in an order for {} shoes", name, legs).into())
}

$ curl localhost:8080/orders/shoes -d '{ "name": "Chashu", "legs": 4 }'
Hello, Chashu! I've put in an order for 4 shoes

Let’s try now with an invalid number of legs (Note that we use the -v flag to use curl in verbose mode).

$ curl -v localhost:8080/orders/shoes -d '{ "name": "Mary Millipede", "legs": 750 }'
< HTTP/1.1 422 Unprocessable Entity
< content-length: 0
< date: Fri, 26 Feb 2021 13:31:17 GMT

We get an http error, 422 to be more specific, and that is because we are using the body_json method to deseriaize the body into the Animal struct and the legs fields type is u8. We will cover body_json and the other available methods for deserialize the body in the Request/Response chapter.