refrakt/validate

Form validation helpers.

All validators are composable functions that accumulate errors as List(#(String, String)) where each tuple is #(field_name, message).

Example

let errors =
  []
  |> validate.required(title, "title", "Title is required")
  |> validate.min_length(title, "title", 3, "Title must be at least 3 characters")
  |> validate.required(body, "body", "Body is required")

Values

confirmation

</>

pub fn confirmation(
  errors: List(#(String, String)),
  value: String,
  confirmation: String,
  field: String,
  message: String,
) -> List(#(String, String))

Check that value equals confirmation, for password and password-repeat fields. The two values are compared as given: no trimming, because passwords may legitimately start or end with a space. Skips the check if the field already has an error.

email

</>

pub fn email(
  errors: List(#(String, String)),
  value: String,
  field: String,
  message: String,
) -> List(#(String, String))

Check that a string looks like an email address.

This is a pragmatic check, not a RFC 5322 parser: the trimmed value must contain exactly one @, a non-empty local part without spaces, and a domain with at least two non-empty dot-separated labels. So "jane@example.com" passes, while "jane", "jane@", "@example.com", "jane@example" and "jane@example..com" fail.

Use it after required so that an empty field reports the “required” message instead of the email message.

float_between

</>

pub fn float_between(
  errors: List(#(String, String)),
  value: String,
  field: String,
  min: Float,
  max: Float,
  message: String,
) -> List(#(String, String))

Check that a string parses as a float between min and max, inclusive on both ends. A value that does not parse as a number fails the check with the same message. Skips the check if the field already has an error.

format

</>

pub fn format(
  errors: List(#(String, String)),
  value: String,
  field: String,
  predicate: fn(String) -> Bool,
  message: String,
) -> List(#(String, String))

Check that a string value matches a format predicate.

inclusion

</>

pub fn inclusion(
  errors: List(#(String, String)),
  value: String,
  field: String,
  allowed: List(String),
  message: String,
) -> List(#(String, String))

Check that a string value matches one of the allowed values.

int_between

</>

pub fn int_between(
  errors: List(#(String, String)),
  value: String,
  field: String,
  min: Int,
  max: Int,
  message: String,
) -> List(#(String, String))

Check that a string parses as an integer between min and max, inclusive on both ends. A value that does not parse as an integer fails the check with the same message. Skips the check if the field already has an error.

max_length

</>

pub fn max_length(
  errors: List(#(String, String)),
  value: String,
  field: String,
  max: Int,
  message: String,
) -> List(#(String, String))

Check that a string value has at most max characters. Skips the check if the field already has an error.

min_length

</>

pub fn min_length(
  errors: List(#(String, String)),
  value: String,
  field: String,
  min: Int,
  message: String,
) -> List(#(String, String))

Check that a string value has at least min characters. Skips the check if the field already has an error (avoids duplicate messages).

required

</>

pub fn required(
  errors: List(#(String, String)),
  value: String,
  field: String,
  message: String,
) -> List(#(String, String))

Check that a string value is not empty (after trimming whitespace).