formal
Type safe HTML form decoding and validation!
gleam add formal
import formal/form
// Define a type that is to be decoded from the form data
pub type SignUp {
SignUp(email: String, password: String)
}
// This function takes the list of key-value string pairs that a HTML form
// produces. It then decodes the form data into a SignUp value, ensuring that
// all the fields are present and valid.
//
pub fn handle_form_submission(values: List(#(String, String))) {
let result =
form.decoding({
use email <- form.parameter
use password <- form.parameter
User(email: email, password: password)
})
|> form.with_values(values)
|> form.field(
"email",
form.string
|> form.and(form.must_not_be_empty)
|> form.and(form.must_be_an_email),
)
|> form.field(
"password",
form.string
|> form.and(form.must_not_be_empty)
|> form.and(form.must_be_string_longer_than(7))
)
|> form.finish
case result {
Ok(data) -> {
// Do something with the SignUp value here
}
Error(form_state) -> {
// Re-render the form with the error messages
}
}
}
An example of using this library with Wisp and Lustre can be found in ./example/.
Further documentation can be found at https://hexdocs.pm/formal.