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 "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.

emailRegex : Regex

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

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

krisajenkins/elm-exts/15.0.0

Exts.Validation

Modules