Re: [Haskelldb-users] Problem using CalendarTimeT column

[Colin P. A. <co...@co...>]

>>>>> "Justin" == Justin Bailey <jgb...@gm...> writes:

    Justin> The type used is not determined by HaskellDB. Your application
    Justin> determines the type it expects, and the appropriate
    Justin> Convertible instance is selected. If that doesn't make
    Justin> sense, what I mean is the type signature of your result
    Justin> determines the type to which the value will be
    Justin> converted. For example, if your function is named
    Justin> "getTimestampRows", you can control the type converted to
    Justin> via it's signature:


    Justin>   getTimestampRows :: IO [Record (Col1 (Expr Day)) ... )]

    Justin> or

    Justin>   getTimestampRows :: IO [Record (Col1 (Expr ZonedTime))
    Justin> ... )]

    Justin> or

    Justin>   getTimestampRows :: IO [Record (Col1 (Expr UTCTime))
    Justin> ... )]

I'm lost here.

HaskellDB is expecting a System.Time.CalendarTime (because I defined
the column as a CalendarT - there was no other choice in the
constructors from FireldDesc), but if I look at
the documentation for System.Time, it says it is deprecated - look at
Data.Time instead.
If I look there, I see Data.Time.Clock.UTCTime, which I guess is what
you are referring to in the line above. But if I try to write such a
record with:

 ct <- getCurrentTime
  DB.insert db IT.imageTable (<snip> # IT.uploadTime <<- ct)

the compiler complains:

  Couldn't match expected type `System.Time.CalendarTime'
           against inferred type `UTCTime'
    In the second argument of `(<<-)', namely `ct'
    In the second argument of `(#)', namely `IT.uploadTime <<- ct'

How do I control this with a signature?
-- 
Colin Adams
Preston Lancashire