Validator
A validation library for Gleam.
This library follows the principle Parse don't validate.
You start with an input type and validate into an output type. These two types can be different. For example:
type UserInput { UserInput(name: Option(String), age: Int) }
type ValidUser { ValidUser(name: String, age: Int) }
Then you create a validator like:
import validator
import validator/common.{ValidatorResult}
import validator/int
import validator/option
fn user_validator(user: UserInput) -> ValidatorResult(ValidUser, String) {
validator.build2(ValidUser)
|> validator.validate(user.name, option.is_some("Please provide a name"))
|> validator.validate(user.age, int.min(13, "Must be at least 13 years old"))
}
And run it:
case user_validator(input) {
Ok(valid_user) -> ...
Error(tuple(first_error, all_errors)) -> ...
}
Error type
Errors can be your own type e.g.
import validator
import validator/common.{ValidatorResult}
import validator/int
import validator/option
type Error {
ErrorEmptyName,
ErrorTooYoung,
}
fn user_validator(user: UserInput) -> ValidatorResult(ValidUser, String) {
validator.build2(ValidUser)
|> validator.validate(user.name, option.is_some(ErrorEmptyName))
|> validator.validate(user.age, int.min(13, ErrorTooYoung))
}
ValidatorResult
ValidatorResult(valid, error)
is an alias for Result(valid, tuple(error, List(error)))
The Ok
branch has the valid output.
The Error
branch has a tuple tuple(error, List(error))
.
The first value is the first error. The second value is a list with all errors (including the first).
Custom property validator
A property validator has two components:
- The error to return
- A function that transforms the property if successful (
fn(input) -> Option(output)
)
Example:
fn bigger_than_10(num: Int) -> Option(num) {
case num > 10 {
True ->
Some(num)
False ->
None
}
}
let custom = validator.custom("Must be bigger than 10", bigger_than_10)
let validator = fn(form: FormInput) {
validator.build1(ValidForm)
|> validator.validate(form.quantity, custom)
}
Test
rebar3 compile
rebar3 eunit
Installation
This package can be installed by adding gleam_validator
to your rebar.config
dependencies:
{deps, [
gleam_validator
]}.