Forms

Browsers have support for client side validation of form data built in. We can use this along with server side validation to give the user a nice experience and ensure security on the back end.

Browser Validation

In the following form we use an email type and a required attribute. The browser will now block form submission until the field is filled in with a valid email address and password.

<form>
  <label for="user_email">Email:</label>
  <input id="user_email" name="email" type="email" required>
  <button>Submit</button>
</form>

We can write this same form using Dioxus. Update crates/ui-components/src/users.rs with a form to add users.

use crate::layout::Layout;
use db::User;
use dioxus::prelude::*;
use web_assets::files::avatar_svg;

// Take a Vec<User> and create an HTML table.
#[component]
pub fn IndexPage(users: Vec<User>) -> Element {
    rsx! {
        Layout {    // <-- Use our layout
            title: "Users Table",
            table {
                thead {
                    tr {
                        th { "ID" }
                        th { "Email" }
                    }
                }
                tbody {
                    for user in users {
                        tr {
                            td {
                                img {
                                    src: format!("/static/{}", avatar_svg.name),
                                    width: "16",
                                    height: "16"
                                }
                                strong {
                                    "{user.id}"
                                }
                            }
                            td {
                                "{user.email}"
                            }
                        }
                    }
                }
            }

            // 👇 this is our new form
            form {
                action: "/sign_up",
                method: "POST",
                label { r#for: "user_email", "Email:" }
                input { id: "user_email", name: "email", r#type: "email", required: "true" }
                button { "Submit" }
            }
        }
    }
}

Note: for and type are Rust keywords. We must prefix them with r# so Rust knows that we want the raw string literal of "for" and "type".

Handling form submission

We need to install serde to transform the HTTP body into a Rust struct.

cd crates/web-server
cargo add [email protected] --features derive

Axum has support for Handlers. We can use those in a lot of different ways and one way is for form implementations. We are going to create a create_form handler to save new users to our database.

Create a new file crates/web-server/src/new_user.rs

use serde::Deserialize;

use crate::errors::CustomError;
use axum::{
    extract::Extension,
    response::Redirect,
    Form,
};

// 👇 create new SignUp struct
#[derive(Deserialize )]
pub struct SignUp {
    email: String,
}

// 👇 handle form submission
pub async fn process_form(
    Extension(pool): Extension<db::Pool>,
    Form(form): Form<SignUp>,
) -> Result<Redirect, CustomError> {
    let client = pool.get().await?;

    let email = form.email;
    let _ = db::queries::users::create_user()
        .bind(&client, &email.as_str())
        .await?;

    // 303 redirect to users list
    Ok(Redirect::to("/"))
}

Add the form handling to our routes

In crates/web-server/main.rs add a mod new_user; and add another route like the following.

.route("/sign_up", post(new_user::process_form))

You'll also need to add post to our use section.

use axum::{extract::Extension, routing::{get, post}, Router};

The compiler will complain becuase we haven't added the database code to handle form submission.

Create the database code

We are using db::queries::users::create_user() in our accept_form handler. We must also update crates/db/queries/users.sql to include our actual SQL query

--: User()

--! get_users : User
SELECT 
    id, 
    email
FROM users;

-- 👇 add `create_user` query
--! create_user
INSERT INTO 
    users (email)
VALUES
    (:email);

You should get results like the screenshot below.

If you add an email to the form and press submit, the server should handle that request and update the users table.

Server Side Validation

Our web form validates that the user input is an email. We should also check that the user input is an email on the server. We can use Validator which will allow us to add validation to the SignUp struct.

Install the Validator crate.

cd crates/web-server
cargo add [email protected] --features derive

Update crates/web-server/src/new_user.rs and add validation.

use serde::Deserialize;
use validator::Validate;

use crate::errors::CustomError;
use axum::{
    extract::Extension,
    http::StatusCode,
    response::{IntoResponse, Redirect, Response},
    Form,
};

#[derive(Deserialize, Validate)]
pub struct SignUp {
    #[validate(email)] // 👈 add validate annotation
    email: String,
}

// 👇 handle form submission
pub async fn process_form(
    Extension(pool): Extension<db::Pool>,
    Form(form): Form<SignUp>,
) -> Result<Response, CustomError> {
    
    // 👇 add our error handling
    if form.validate().is_err() {
        return Ok((StatusCode::BAD_REQUEST, "Bad request").into_response());
    }

    let client = pool.get().await?;

    let email = form.email;
    let _ = db::queries::users::create_user()
        .bind(&client, &email.as_str())
        .await?;

    // 303 redirect to users list
    Ok(Redirect::to("/").into_response())
}

And we can test that our validation works by sending a request directly to the server (bypassing the browser form):

curl http://localhost:3000/sign_up --data-raw 'email=bad-data'