Re: [Haskelldb-users] Problem using CalendarTimeT column

[Justin B. <jgb...@gm...>]

The generated module is what I wanted. Here is your table definition:

> type ImageTable =
>    (RecCons IndexNumber (Expr Integer)
>     (RecCons Caption (Expr String)
>      (RecCons Thumbnail (Expr String)
>       (RecCons Preview (Expr String)
>        (RecCons Original (Expr (Maybe String))
>         (RecCons UploadTime (Expr CalendarTime) RecNil))))))

Specifically, UploadTime is of tyep "CalendarTime". The error you got was:

>  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'

The solution is to make "ct" have type CalendarTime, not UTCTime.
HaskellDB uses the deprecated, but still in wide use, old-time package
which exposes System.Time.CalendarTime. You can't get a CalendarTime
for the current date direclty, but you can indirectly. Try:

  clockTime <- getClockTime
  ct <- toCalendarTime clockTime

Or more succinctly:

  ct <- getClockTime >>= toCalendarTime

Then you should be able to do your insert. Finally, you asked:

> How do I control this with a signature?

That's not relevant here as I was referring to the conversion of SQL
types to Haskell values. Since DBDirect generates the code for your
table, you are stuck with CalendarTime.

DBDirect is just a convenience, though. You could make your own
definition by hand. There is also the haskelldb-th package, which
gives some Template Haskell functions for defining tables and columns.
Just FYI.

Justin