Elm如何更新表头

type alias TableHeader =
    { title : String
    , sortOrder : SortOrder
    }

type alias Model =
    { tableHeaders : List TableHeader
    , ...
    }

type Msg
    = UpdateTableHeader Int TableHeader
    ...

view : Model -> Html Msg
view model =
    ...
    table []
        [ thead []
            [ tr []
                (List.map renderTableHeader model.tableHeaders)
            ]
        ...
        ]
    ...

renderTableHeader : TableHeader -> Html Msg
renderTableHeader header =
    th []
        [ text header.title
        , button [ onClick (UpdateTableHeader index updatedHeader) ] [ text "Sort" ]
        ]

update : Msg -> Model -> ( Model, Cmd Msg )
update msg model =
    case msg of
        UpdateTableHeader index updatedHeader ->
            let
                updatedHeaders =
                    List.indexedMap (\i header -> if i == index then updatedHeader else header) model.tableHeaders
            in
            ( { model | tableHeaders = updatedHeaders }, Cmd.none )
        ...