validated
Easily accumulate errors in Gleam!
import gleam/string
import validated.{type Validated, Valid}
import validated as v
pub opaque type Form {
Form(email: String, age: Int)
}
pub fn valid_form(email: String, age: Int) -> Result(Form, List(String)) {
do_valid_form(email, age) |> v.to_result
}
fn do_valid_form(email: String, age: Int) -> Validated(Form, String) {
use email, _ <- v.do(validate_email(email))
use age, _ <- v.do(validate_age(age))
Valid(Form(email:, age:))
}
fn validate_email(email: String) -> Validated(String, String) {
case string.contains(email, "@") {
True -> Ok(email)
False -> Error("email addresses must include '@'")
}
|> v.string
}
fn validate_age(age: Int) -> Validated(Int, String) {
case age >= 18 {
True -> Ok(age)
False -> Error("you must be 18 or older")
}
|> v.int
}
pub fn main() {
let assert Ok(Form("lucy@example.com", 18)) =
valid_form("lucy@example.com", 18)
let assert Error(["email addresses must include '@'"]) =
valid_form("lucy", 18)
let assert Error([
"email addresses must include '@'",
"you must be 18 or older",
]) = valid_form("lucy", 1)
}
Further documentation can be found at https://hexdocs.pm/validated.
Development
gleam run # Run the project
gleam test # Run the tests