[英]Modifying form submission data before it gets sent to stringRead
我有一個Digestive Functors表單,如下所示:
dateTimeForm :: Monad m => Maybe LocalTime -> Form Text m LocalTime
dateTimeForm t = LocalTime
<$> "date" .: stringRead "Must be a valid date" (localDay <$> t)
<*> "time" .: stringRead "Must be a valid time" (localTimeOfDay <$> t)
我用於此表單的輸入元素是<input type="date" />
和<input type="time" />
。 這適用於此表單的日期部分,但在時間部分不太好。 支持時間輸入元素的瀏覽器僅提交小時和分鍾(例如“18:00”),但TimeOfDay需要小時,分鍾和秒。 這會導致stringRead失敗並且Digestive Functors向用戶報告錯誤(“必須是有效時間”)。
我嘗試解決這個問題,但如果用戶提交的時間無效,他們就不會再從Digestive Functors中獲得一個有吸引力的錯誤(Prelude.read:no parse)。
dateTimeForm :: Monad m => Maybe LocalTime -> Form Text m LocalTime
dateTimeForm t = toLocalTime
<$> "date" .: stringRead "Must be a valid date" (localDay <$> t)
<*> "time" .: string (show . localTimeOfDay <$> t)
where
toLocalTime d x = LocalTime d $ read $ if length x == 8 then x else x <> ":00"
我想我要找的是validate
功能和maybeRead
的一些幫助。 這似乎有效:
dateTimeForm :: Monad m => Maybe LocalTime -> Form Text m LocalTime
dateTimeForm t = LocalTime
<$> "date" .: stringRead "Must be a valid date" (localDay <$> t)
<*> "time" .: validate validTime (string (show . localTimeOfDay <$> t))
where
-- the time input element only submits hours and minutes ("18:00"), which is 5 characters long
validTime x = case maybeRead (if length x == 5 then x <> ":00" else x) of
Just x' -> Success x'
_ -> Error "Must be a valid time"
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