This library provides a datatype to model and validate input field data.

To use this data type, let's say that you need a sign up form that has a requried name field, a required email field, and an age field that must be between 18 & 100 that you need to send to your server after it's validated.

First, you can import the package and create the fields in your model

... other imports
import Field as F
import Field.Int as FInt
import Field.String as FStr


type alias Model =
    { name : FStr.Field
    , email : FStr.Field
    , age : FInt.Field
    }




init : ( Model, Cmd Msg )
init =
    { name = F.init ""
    , email = F.init ""
    , age = F.init 0
    }
        ! []

Then, you add a few messages to update the fields, and one to submit your form

type Msg
    = SetNameField String
    | SetEmailField String
    | SetAgeField String
    | Submit

Next, you add logic to set & validate the fields to your update function

update : Msg -> Model -> ( Model, Cmd Msg )
update msg model =
    case msg of
        SetNameField value ->
            { model
                | name =
                    value
                        |> F.resetValue model.name
                        |> validateName
            }
                ! []


        SetEmailField value ->
            { model
                | email =
                    value
                        |> F.resetValue model.email
                        |> validateEmail
            }
                ! []


        SetAgeField value ->
            { model
                | age =
                    value
                        |> (String.toInt >> Result.withDefault 0)
                        |> F.resetValue model.age
                        |> validateAge
            }
                ! []


        Submit ->
            let
                name =
                    validateName model.name


                email =
                    validateEmail model.email


                age =
                    validateAge model.age


                cmds =
                    case ( F.toResult name, F.toResult email, F.toResult age ) of
                        ( Ok nameValue, Ok emailValue, Ok ageValue ) ->
                            [ ... some command ... ]


                        _ ->
                            []
            in
            { model
                | name = name
                , email = email
                , age = age
            }
                ! cmds




validateName : FStr.ValidationFunc
validateName =
    FStr.notEmpty




validateEmail : FStr.ValidationFunc
validateEmail =
    FStr.notEmpty >> FStr.email




validateAge : FInt.ValidationFunc
validateAge =
    FInt.greaterThanOrEqual 18 >> FInt.lessThan 100

Finally, wire it into the view!

view : Model -> Html Msg
view model =
    Html.div []
        [ Html.h1 [] [ Html.text "Sign Up!" ]
        , F.view (stringFieldConfig "Name" SetNameField) model.name
        , F.view (stringFieldConfig "Email" SetEmailField) model.email
        , F.view (intFieldConfig "Age" SetAgeField) model.age
        , Html.button [ Html.Events.onClick Submit ]
            [ Html.span [] [ Html.text "Submit" ] ]
        ]


stringFieldConfig : String -> (String -> msg) -> FStr.ViewConfig msg
stringFieldConfig title toMsg =
    { valid =
        \meta value ->
            Html.div []
                [ Html.input
                    [ Html.Events.onInput toMsg
                    , Html.Attributes.value value
                    , Html.Attributes.disabled meta.disabled
                    ]
                    []
                ]
    , invalid =
        \meta value errorMessage ->
            Html.div []
                [ Html.input
                    [ Html.Events.onInput toMsg
                    , Html.Attributes.value value
                    , Html.Attributes.disabled meta.disabled
                    ]
                    []
                , Html.span []
                    [ Html.text errorMessage ]
                ]
    }


intFieldConfig : String -> (String -> msg) -> FInt.ViewConfig msg
intFieldConfig title toMsg =
    { valid =
        \meta value ->
            Html.div []
                [ Html.input
                    [ Html.Events.onInput toMsg
                    , Html.Attributes.value (toString value)
                    , Html.Attributes.type_ "number"
                    , Html.Attributes.disabled meta.disabled
                    ]
                    []
                ]
    , invalid =
        \meta value errorMessage ->
            Html.div []
                [ Html.input
                    [ Html.Events.onInput toMsg
                    , Html.Attributes.value (toString value)
                    , Html.Attributes.type_ "number"
                    , Html.Attributes.disabled meta.disabled
                    ]
                    []
                , Html.span []
                    [ Html.text errorMessage ]
                ]
    }

In this example, we only use the built-in validators, but it's pretty simple to create your own validators too! Take a look at an example to see a similar example to the one above but with a custom validator.

Base

Viewing fields

Interacting with fields

Validation