Elm:有条件的 PreventDefault (内容可编辑)

Question

我正在尝试制作一个内容可编辑标签，使用 enter 来更新模型。

我的代码如下，这是一个您可以在 Ellie 上使用的版本。 。

当您点击离开时，“模糊”属性会起作用并更新模型。但我希望在按下 enter 时获得相同的“更新”功能。

view : Model -> Html Msg
view model =
    let
        attrs =
            [ contenteditable True
              --, on "blur" (Json.map UpdateTitle targetTextContent)
            , onInput2 UpdateTitle
            , onEnter EnterPressed
            , id "title"
            , class "title"
            ]
    in
        div []
            [ h1 attrs [ text model.existing ]
            , text "Click above to start editing. Blur to save the value. The aim is to capture an <enter> and interpret that as a blur, i.e. to save the value and blur the field"
            , p [] [ text <| "(" ++ model.existing ++ ")" ]
            ]


targetTextContent : Json.Decoder String
targetTextContent =
    Json.at [ "target", "textContent" ] Json.string


onInput2 : (String -> msg) -> Attribute msg
onInput2 msgCreator =
    on "input" (Json.map msgCreator targetTextContent)


onEnter : (Bool -> msg) -> Attribute msg
onEnter enterMsg =
    onWithOptions "keydown"
        { stopPropagation = False
        , preventDefault = False
        }
        (keyCode
            |> Json.andThen
                (\ch ->
                    let
                        _ =
                            Debug.log "on Enter" ch
                    in
                        Json.succeed (enterMsg <| ch == 13)
                )
        )

这段代码似乎可以正常更新模型，但 DOM 变得困惑。例如，如果我在“blast”后输入 enter，我会看到此内容

我尝试切换到 Html.Keyed 并使用“keydown”，但它没有任何区别或只是产生了不同的问题。

Answer 1

解决了!关键点是使用 Json.Decode.fail 的过滤函数，这样只有 <enter>受 PreventDefault 约束。请参阅https://github.com/elm-lang/virtual-dom/issues/18#issuecomment-273403774对于这个想法。

view : Model -> Html Msg
view model =
    let
        attrs =
            [ contenteditable True
            , on "blur" (Json.map UpdateTitle targetTextContent)
            , onEnter EnterPressed
            , id "title"
            , class "title"
            ]
    in
        div []
            [ h1 attrs [ text model.existing ]
            , text "Click above to start editing. Blur to save the value. The aim is to capture an <enter> and interpret that as a blur, i.e. to save the value and blur the field"
            , p [] [ text <| "(" ++ model.existing ++ ")" ]
            ]


targetTextContent : Json.Decoder String
targetTextContent =
    Json.at [ "target", "textContent" ] Json.string


onEnter : msg -> Attribute msg
onEnter msg =
    let
        options =
            { defaultOptions | preventDefault = True }

        filterKey code =
            if code == 13 then
                Json.succeed msg
            else
                Json.fail "ignored input"

        decoder =
            Html.Events.keyCode
                |> Json.andThen filterKey
    in
        onWithOptions "keydown" options decoder