给定IANA时区和本地时间，将其解析为Maybe Posix？

Question

有没有办法在Elm中使用当地时间（例如字符串2019-03-18T09:10:12.4;没有指定偏移量）和时区（例如Australia/Sydney）到可能的Posix值（即转换为UTC的时间），而不使用端口？

---

有waratuman/time-extra，但它似乎只适用于Date部分。令人遗憾的是rtfeldman/elm-iso8601-date-strings不接受timezones。

在JS中，有诸如moment-tz和date-fns-timezone之类的选项，但是避免JS interop进行频繁的日期解析会更简单。

Answer 1

通过组合justinmimbs/time-extra和justinmimbs/timezone-data，您应该能够在Elm中完全获得有效的posix。

但是：Kua zxsw指出

---

首先，你需要将你的https://ellie-app.com/54tyw9yvsQga1转换为timestampWithoutTimezone：

Parts

然后，使用

toParts : String -> Maybe Parts
toParts timestampWithoutTimezone =
    timestampWithoutTimezone
        |> Regex.find regex
        |> List.map .submatches
        |> List.head
        |> Maybe.andThen Maybe.Extra.combine
        |> Maybe.andThen listToParts

regex : Regex
regex =
    Maybe.withDefault Regex.never <|
        Regex.fromString "^(\\d{4})-(\\d{2})-(\\d{2})T(\\d{2}):(\\d{2}):(\\d{2})\\.(\\d)$"


monthLookup : Dict String Month
monthLookup =
    Dict.fromList [ ( "01", Jan ), ( "02", Feb ), ( "03", Mar ), ( "04", Apr ), ( "05", May ), ( "06", Jun ), ( "07", Jul ), ( "08", Aug ), ( "09", Sep ), ( "10", Oct ), ( "11", Nov ), ( "12", Dec ) ]


listToParts : List String -> Maybe Parts
listToParts list =
    let
        toInt : Int -> Maybe Int
        toInt index =
            list |> List.Extra.getAt index |> Maybe.andThen String.toInt
    in
    Maybe.map2 Parts
        (toInt 0)
        (list |> List.Extra.getAt 1 |> Maybe.andThen (\month -> Dict.get month monthLookup))
        |> Maybe.andThen (\parts -> Maybe.map5 parts (toInt 2) (toInt 3) (toInt 4) (toInt 5) (toInt 6))

和适当的partsToPosix，你可以得到一个posix值：

Zone

库作者建议您在模型中存储已评估的区域值：

toPosix : Time.Zone -> String -> Maybe Posix
toPosix zone timestampWithoutTimezone =
    timestampWithoutTimezone
        |> toParts
        |> Maybe.map (Time.Extra.partsToPosix zone)

Answer 2

如果我们可以假设您的所有日期都没有时区，并且您总是希望在将它们转换为Posix之前将它们转换为

model = { zone = TimeZone.australia__sydney () }

toPosix model.zone "2019-03-18T09:10:12.4"

，那么您应该能够自己连接偏移以创建Australia/Sydney：

2019-03-18T09:10:12.4+11:00