我意识到我必须在某个地方缺少一个参数，或者我的一个参数不正确，但是在尝试了所有我能想到的东西之后，我不确定该怎么做。
handleKeyDown : msg -> Attribute (Int -> Msg)
handleKeyDown message =
custom "keydown" (Json.succeed { message = KeyPressed, stopPropagation = True, preventDefault = True })
view : Model -> Html Msg
view model =
div []
[ input
[ handleKeyDown ]
[ text "" ]
]
错误
The 1st argument to `input` is not what I expect:
104| [ input
105|> [ handleKeyDown ]
106| [ text "" ]
This argument is a list of type:
List #(msg -> Attribute (Int -> Msg))#
But `input` needs the 1st argument to be:
List #(Attribute msg)#
答案 0 :(得分：5)
这里有几个问题：
<link href="https://cdn.datatables.net/1.10.19/css/jquery.dataTables.min.css" rel="stylesheet"/>
<script src="https://code.jquery.com/jquery-3.3.1.js"></script>
<script src="https://cdn.datatables.net/1.10.19/js/jquery.dataTables.min.js"></script>
<table id="trainings-table">
<thead>
<tr>
<th data-name="name">description</th>
<th data-name="status">Status</th>
<th data-name="date">date</th>
<th date-name="duration">days</th>
</tr>
</thead>
<tbody>
<!-- Expected behaviour: This row below should be hidden after initialization -->
<tr>
<td>Training 1</td>
<td>Completed</td>
<td>28.04.2019</td>
<td>1 day</td>
</tr>
<!-- Expected behaviour: Only show row below after initialization -->
<tr>
<td>Training 2</td>
<td>Planned</td>
<td>05.05.2019</td>
<td>2 days</td>
</tr>
</tbody>
</table>需要一个handleKeyDown参数，您不会使用它，也不会传递它。因此，类型为message，而不是预期的msg -> Attribute ...。
Attribute ...似乎具有类型KeyPressed的有效负载。因此，返回值为Int而不是Attribute (Int -> Msg)。
假设您要使用Attribute Msg参数并从事件中获取message，这应该可以工作：
keyCode在这里，handleKeyDown : (Int -> Msg) -> Html.Attribute Msg
handleKeyDown tag =
let
options message =
{ message = message
, stopPropagation = True
, preventDefault = True
}
decoder =
Json.field "keyCode" Json.int
|> Json.map tag
|> Json.map options
in
Html.Events.custom "keydown" decoder
view : Model -> Html Msg
view model =
div []
[ input
[ handleKeyDown KeyPressed ]
[ text "" ]
]
期望带有有效负载handleKeyDown的标签/消息。内部事件解码器检索Int，将其包装在您传入的标签中，然后使用keyCode将其包装在options对象中。
但是请注意，preventDefault = True已过时，您可能想使用keyCode或code，它们都是字符串。