Represents a form field.

It contains:

• the current value of the field
• an update function that takes a new field value and returns updated form values
• the attributes of the field

These record fields are normally used in view code to set up the value and onInput attributes. For example, you could render a TextField like this:

view : (values -> msg) -> Form values output -> values -> Html output
view onChange form values =
    let
        { fields, result } =
            Form.fill form values


        fieldsHtml =
            List.map (viewField onChange) fields


        -- ...
    in
    Html.form
        [-- ...
        ]
        [ Html.div [] fieldsHtml
        , submitButton
        ]


viewField : (values -> msg) -> ( Form.Field values, Maybe Error ) -> Html msg
viewField onChange ( field, maybeError ) =
    case field of
        Form.Text TextField.Raw { value, update, attributes } ->
            Html.input
                [ Attributes.type_ "text"
                , Attributes.value
                    (value
                        |> Value.raw
                        |> Maybe.withDefault ""
                    )
                , Attributes.onInput (update >> onChange)
                , Attributes.placeholder attributes.placeholder
                ]
                []


        _ ->
            -- ...