Elm 从列表中查找一项

榆树新来的。。 我正在尝试从列表中获取一项

这是模型（第一次发布时忘记） 我假设Report.id必须是Int

-- MODEL


type alias Model =
    { reports : List Report
    , alertMessage : Maybe String
    }


type alias Report =
    { id : Int
    , city : String
    , country : String
    }


initialModel : Model
initialModel =
    { reports = []
    , alertMessage = Nothing
    }


-- UPDATE


type Msg
= NewReports (Result Http.Error (List Report))
  | ShowReport
  | CloseAlert

update : Msg -> Model -> ( Model, Cmd Msg )
update msg model =
case msg of
    NewReports (Ok weatherReports) ->
        ( { model | reports = weatherReports }, Cmd.none )

    NewReports (Err error) ->
        ( { model | alertMessage = Just (httpErrorToMessage error) }, Cmd.none )

    CloseAlert ->
        ( { model | alertMessage = Nothing }, Cmd.none )

    ShowReport model ->
        ( ??? )

--VIEW now more complete to get the right picture

viewReportRow : Report -> Html Msg
viewReportRow report =
    tr []
        [ td [] [ text report.city ]
        , td [] [ text report.country ]
        , td [] []
            [ button
             [ class "button primary small"
             , onClick (ShowReport report.id)
             ]
             [ text "Show"]
             ]
        ]

如何正确地从按钮发送id，并在列表中筛选具有此id的条目

感谢您的支持

给您 我更新了ShowReport消息以获取id（我假设是字符串），演示了如何进行筛选（由您决定如何处理生成的列表），并将视图片段转换为可以映射到model.reports的函数

这只是指示性的，因为您没有提供模型的太多细节

type Msg
    = NewReports (Result Http.Error (List Report))
      | ShowReport String
      | CloseAlert

update : Msg -> Model -> ( Model, Cmd Msg )
update msg model =
case msg of
    NewReports (Ok weatherReports) ->
        ( { model | reports = weatherReports }, Cmd.none )

    NewReports (Err error) ->
        ( { model | alertMessage = Just (httpErrorToMessage error) }, Cmd.none )

    CloseAlert ->
        ( { model | alertMessage = Nothing }, Cmd.none )

    ShowReport id ->
        let report = 
            List.filter (\rep -> rep.id == id) model.reports
        in 
        (model, Cmd.none)

--VIEW

mkShowItem id =
    td []
        [
        button
        [ class "button small"
        , onClick (ShowReport id)
        ]
        [ text "Show"]
        ]

给你 我更新了ShowReport消息以获取id（我假设是字符串），演示了如何进行筛选（由您决定如何处理生成的列表），并将视图片段转换为可以映射到model.reports的函数

这只是指示性的，因为您没有提供模型的太多细节

type Msg
    = NewReports (Result Http.Error (List Report))
      | ShowReport String
      | CloseAlert

update : Msg -> Model -> ( Model, Cmd Msg )
update msg model =
case msg of
    NewReports (Ok weatherReports) ->
        ( { model | reports = weatherReports }, Cmd.none )

    NewReports (Err error) ->
        ( { model | alertMessage = Just (httpErrorToMessage error) }, Cmd.none )

    CloseAlert ->
        ( { model | alertMessage = Nothing }, Cmd.none )

    ShowReport id ->
        let report = 
            List.filter (\rep -> rep.id == id) model.reports
        in 
        (model, Cmd.none)

--VIEW

mkShowItem id =
    td []
        [
        button
        [ class "button small"
        , onClick (ShowReport id)
        ]
        [ text "Show"]
        ]

---

谢谢你的支持，西蒙。我用丢失的模型完成了代码。。ShowReport仍然抛出错误“model.reports”似乎不够。function

filter

的第二个参数导致不匹配。78 | List.filter（\item->item==id）model.reports^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^。我用丢失的模型完成了代码。。ShowReport仍然抛出错误“model.reports”似乎不够。function

filter

的第二个参数导致不匹配。78 | List.filter（\item->item==id）model.reports^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^