select.elm

import Html exposing (..)
import Html.App exposing (..)
import Html.Events exposing (..)
import Json.Decode exposing (Decoder, customDecoder, string)


main =
  beginnerProgram { model = English, view = view, update = update }


{-| Currently supported languages. -}
type Language
    = English
    | Japanese


{-| A JSON decoder of Language. -}
languageDecoder : Decoder Language
languageDecoder =
    customDecoder targetValue fromStringLanguage


fromStringLanguage : String -> Result String Language
fromStringLanguage str =
    case str of
        "English" -> Ok English
        "Japanese" -> Ok Japanese
        other -> Err ("Invalid language: " ++ other)


-- MODEL

type alias Model = Language


-- UPDATE

type Msg
    = Change Language

update : Msg -> Model -> Model
update msg model =
    case msg of
        Change language -> language


-- VIEW

view : Model -> Html Msg
view model =
    Html.form []
        [ select [ on "change" <| Json.Decode.map Change languageDecoder ]
            (List.map (viewOption model) ["English", "Japanese"])
        , text (toString model)
        ]
        
        
viewOption : Model -> String -> Html Msg
viewOption model s =
  option [] [ text s ]