有条件地在Elm的表单提交上切换`preventDefault`

,onWithOptions
    "submit"
    (if model.name == "" then
        (Debug.log "prevent" { preventDefault = True,stopPropagation = True })
      else
        (Debug.log "allow" { preventDefault = False,stopPropagation = False })
    )
    (Json.succeed FormSubmit)

更新了答案的结果

正如@Tosh所说,隐藏按钮可以解决问题：

,button
    [ onPreventClickHtml FormSubmit,Html.Attributes.hidden (model.name == "" |> not) ]
    [ text " prevent" ],button
    [ onClick FormSubmit,Html.Attributes.hidden (model.name == "") ]
    [ text "allow" ]

onPreventClickHtml在哪里：

onPreventClickHtml : Msg -> Attribute Msg
onPreventClickHtml msg =
    onWithOptions
        "click"
        { preventDefault = True,stopPropagation = True }
        (Json.succeed msg)

有条件地显示按钮不起作用：

,(if model.name == "" then
    button
        [ onPreventClickHtml FormSubmit ]
        [ text " prevent" ]
  else
    button
        [ type' "submit",onClick FormSubmit ]
        [ text "allow" ]
  )

我正在使用elm-mdl,因此发现实施解决方案更具挑战性,因为根据我的经验创建自定义onclick需要elm-mdl未公开的类型,因此需要重复.

,if model.name == "" then
    Material.Options.nop
  else
    Material.Options.css "visibility" "hidden",onPreventClick FormSubmit,if model.name == "" then
    Material.Options.css "visibility" "hidden"
  else
    Material.Options.nop,Button.onClick FormSubmit



onPreventClick : Msg -> Property Msg
onPreventClick message =
    Material.Options.set
        (options -> { options | onClick = Just (onPreventClickHtml message) })

-- Duplicated from elm-mdl
type alias Property m =
    Material.Options.Property (Config m) m

-- Duplicated from elm-mdl
type alias Config m =
    { ripple : Bool,onClick : Maybe (Attribute m),disabled : Bool,type' : Maybe String
    }

另一种适用于我的场景的方法是更改??按钮类型：

,if model.name == "" then
    Button.type' "reset"
  else
    Button.type' "submit"