Exts.Validation

Simple tools for validation. See also Richard Feldman's elm-validate

apply : Result e (a -> b) -> Result e a -> Result e b

A validator is a function that takes a possibly-invalid form, and either returns an error message, or a form that is definitely valid. For example:

type alias Form =
  { email : Maybe String
  , age : Maybe Int
  }


type alias ValidForm =
  { email : String
  , age : Int
  }


validateForm : Form -> Result String ValidForm
validateForm form =
  Ok ValidForm
    |: notBlank "Message is required and may not be blank." form.message
    |: matches emailRegex "Email is required and may not be blank." form.email
    |: required "Age is required" form.age

An error message is typically a String, but may be any type you choose.

(Hat tip to CircuitHub, who inspired the syntax and guided the code with their elm-json-extra library.)

(|:) : Result e (a -> b) -> Result e a -> Result e b

Convenient synonym for apply.

required : e -> Maybe a -> Result e a

A field that might be Nothing, but is only valid if it is Just a.

notBlank : e -> Maybe String -> Result e String

A field that might be Nothing, but is only valid if it is a non-empty String.

matches : Regex -> e -> Maybe String -> Result e String

A field that must match the given regex.

emailRegex : Regex

A basic email regex. This is incredibly simplistic, but is included for convenience.

Use it like:

Remember that the only real way to validate an email address is to send something to it and get a reply.

krisajenkins/elm-exts/19.4.0

Exts.Validation

Modules