sras / th-opaleye

th-opaleye

This is a Template Haskell lib that generates boilerplates that helps to work with Opaleye.

You need to put the configuration for this in another haskell file, and import it in the main file where you are going to make the calls to the TH functions

So this can be your Main.hs file

  import OpaleyeThConfig

  makeOpaleyeModels (connectInfo, options)
  makeAdaptorAndInstances (connectInfo, options)
  makeOpaleyeTables (connectInfo, options)

The arguments to the functions are the postgresqlSimple's connectInfo and options which is of type

data Options = Options { tableOptions :: [(String, TableOptions)] }

The first element of tuple is the table name and TableOptions is defined as

data TableOptions = TableOptions { modelName :: String, overrideDefaultTypes :: [(String, String)], protectedFields :: [String] }

The modelName is the name of the Haskell type of this table.

The overrideDefaultTypes field lists fields that should be mapped to a custom datatype, and is a tuple of format (db_column_name, newtype_name)

The protectedFields field is used to denote fields that should only get getters, when generating lenses.

A sample OpaleyeTHConfig.hs file

import Opaleye.TH
import Database.PostgreSQL.Simple

options = Options [
   ("users", usersOptions),   
   ("products", productsOptions)
  ]

usersOptions = TableOptions {
  modelName = "User",
  overrideDefaultTypes = [
    ("key", "UserId"),
    ("email", "Email")
  ],
  protectedFields = ["email"]
}

productsOptions = TableOptions {
  modelName = "Product",
  overrideDefaultTypes = [
    ("key", "ProductId"),
    ("user_id", "UserId")
  ],
  protectedFields = []
}

connectInfo = defaultConnectInfo { connectPassword = "postgres", connectDatabase = "scratch"}