On Wed, Jun 29, 2011 at 11:17 AM, Kamil Ciemniewski
Hi all,
I've got some "newbie" problems using MongoDB as backend in Persistent.
Basically I've got my app type defined as: data MyApp = MyApp { getStatic :: Static -- ^ Settings for static file serving. , connPool :: ConnPool Host }
And I made it an instance of YesodPersist by: instance YesodPersist MyApp where type YesodDB MyApp = MongoDBReader Host runDB db = liftIOHandler $ fmap connPool getYesod >>= (\p -> return (p, "localhost")) >>= runMongoDBConn db
And I made it an instance of YesodAuth as well by: instance YesodAuth MyApp where type AuthId MyApp = UserId
loginDest _ = RootR logoutDest _ = RootR
getAuthId creds = runDB $ do x <- getBy $ UniqueUser $ credsIdent creds case x of Just (uid, _) -> return $ Just uid Nothing -> do fmap Just $ insert $ User (credsIdent creds) Nothing
authPlugins = [ authEmail ]
I've defined User model as yesod scaffold tool defines it.
Now, when I try to compile it i get:
No instances for (Control.Monad.Context.Context Database.MongoDB.Connection.MasterOrSlaveOk (GGHandler s MyApp IO), Control.Monad.Context.Context Database.MongoDB.Query.Database (GGHandler s MyApp IO), Control.Monad.Context.Context Database.MongoDB.Internal.Protocol.Pipe (GGHandler s MyApp IO), Control.Monad.Context.Context Database.MongoDB.Query.WriteMode (GGHandler s MyApp IO), Control.Monad.Throw.Throw Database.MongoDB.Query.Failure (GGHandler s MyApp IO)) arising from a use of `insert' Possible fix: add instance declarations for (Control.Monad.Context.Context Database.MongoDB.Connection.MasterOrSlaveOk (GGHandler s MyApp IO), Control.Monad.Context.Context Database.MongoDB.Query.Database (GGHandler s MyApp IO), Control.Monad.Context.Context Database.MongoDB.Internal.Protocol.Pipe (GGHandler s MyApp IO), Control.Monad.Context.Context Database.MongoDB.Query.WriteMode (GGHandler s MyApp IO), Control.Monad.Throw.Throw Database.MongoDB.Query.Failure (GGHandler s MyApp IO)) In the expression: insert In the second argument of `($)', namely `insert $ User (credsIdent creds) Nothing' In the expression: fmap Just $ insert $ User (credsIdent creds) Nothing
The problem is probably very trivial.. But I've got no ideas how to fix it.
Best regards Kamil Ciemniewski
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I don't have direct experience with the MongoDB backend, but I can give this a shot if I saw some code. I think one possibility would be to wrap everything in a liftIO, but then you won't have access to the Handler monad features. This would prevent you from doing things like setting messages and sending redirects from the database access itself, but should otherwise be fine. Michael