using yesod's persistent.

Model.hs

{-# LANGUAGE EmptyDataDecls             #-}
{-# LANGUAGE FlexibleContexts           #-}
{-# LANGUAGE GADTs                      #-}
{-# LANGUAGE GeneralizedNewtypeDeriving #-}
{-# LANGUAGE MultiParamTypeClasses      #-}
{-# LANGUAGE OverloadedStrings          #-}
{-# LANGUAGE QuasiQuotes                #-}
{-# LANGUAGE TemplateHaskell            #-}
{-# LANGUAGE TypeFamilies               #-}

module Model where

import Control.Monad.IO.Class  (liftIO)
import Control.Monad.Logger    (runStderrLoggingT)
import Database.Persist
import Database.Persist.Postgresql
import Database.Persist.TH
import Data.Time
import Data.Int

share [mkPersist sqlSettings, mkMigrate "migrateAll"] [persistLowerCase|
User
    email String
    alias String
    image_url String
    show_email Bool
    UniqueEmail email
    date UTCTime default=CURRENT_TIME
    deriving Show
Post
    atom Int
    material String
    processing String
    params String
    image_url String
    reference String
    owner UserId
    material_url String
    date UTCTime default=CURRENT_TIME
    deriving Show
|]

connStr = "host=localhost dbname=communis-db user=communis password=develPassword port=5432"

new_user :: User -> IO ()
new_user(User email alias image_url show_email _) = runStderrLoggingT $ withPostgresqlPool connStr 10 $ \pool -> liftIO $ do
    flip runSqlPersistMPool pool $ do
        runMigration migrateAll
        now <- liftIO getCurrentTime
        usrid <- insert $ User email alias image_url show_email now
        usr <- get usrid
        liftIO $ print usr

update_user :: String -> User -> IO()
update_user em u = runStderrLoggingT $ withPostgresqlPool connStr 10 $ \pool -> liftIO $ do
    flip runSqlPersistMPool pool $ do
        runMigration migrateAll
        usr <- getBy $ UniqueEmail em
        case usr of
          Just (Entity userId user) -> replace userId user
{-
delete_user :: Int64 -> IO ()
delete_user i = runStderrLoggingT $ withPostgresqlPool connStr 10 $ \pool -> liftIO $ do
    flip runSqlPersistMPool pool $ do
        runMigration migrateAll
        delete (toSqlKey i)
-}

new_post :: Post -> IO ()
new_post (Post atom material processing params image_url reference owner material_url _) = runStderrLoggingT $ withPostgresqlPool connStr 10 $ \pool -> liftIO $ do
    flip runSqlPersistMPool pool $ do
        runMigration migrateAll
        now <- liftIO getCurrentTime
        postId <- insert $ Post atom material processing params image_url reference owner material_url now
        post <- get postId
        liftIO $ print post

update_post :: Int64 -> Post -> IO()
update_post id post = runStderrLoggingT $ withPostgresqlPool connStr 10 $ \pool -> liftIO $ do
    flip runSqlPersistMPool pool $ do
        runMigration migrateAll
        replace (toSqlKey id) post