Hi,
I'm developing toy application to learn HDBC. I have "problem" with
doing relations mapping. Actually I don't know is it a problem or
"feature". ;)
Anyway, I have two tables with relation between them:
(this example is simplified to the whole structure of database, you can imagine)
CREATE TABLE TD_set (
setId INTEGER PRIMARY KEY,
setName TEXT NOT NULL
)
CREATE TABLE TO_card (
cardId INTEGER PRIMARY KEY AUTOINCREMENT,
setId INTEGER NOT NULL," -- Relation to TD_set
setSeq INTEGER NOT NULL
)
(no foreign key as sqlite3 does not care anyway - at least AFAIK)
And in Haskell:
> type CardSet = String
>
> data Card = Card {
> set :: CardSet,
> seqNo :: Integer,
> }
There is no problem with filling the structure Card with "seqNo" but I
can't fill "set". I would have to put there IO (CardSet) but I don't
want to do that as whole structure returned from my mapping function
is already inside IO monad. Can I do it?
Here is my (perfect) function - http://hpaste.org/5839 . See
"getCards" and some helper functions. This does not compile as (I
believe) getElement wants to return IO (CardSet)
Thank you in advance for all your input.
Radek.
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