groundhog-converters

Extended Converter Library for groundhog embedded types

Latest on Hackage:0.1.0

This package is not currently in any snapshots. If you're interested in using it, we recommend adding it to Stackage Nightly. Doing so will make builds more reliable, and allow stackage.org to host generated Haddocks.

BSD3 licensed and maintained by Scott Murphy

groundhog-converters

Groundhog allows a programmer to represent a haskell datatype by an equivalent type that is more suited for Database work. groundhog-converters provides a selection of common converters that have proved useful.

Usage

-- | Sample DataType 'Group' proviides a Map between an Integer and  a 'Person'
-- However, the person is embedded in the Datatype relative to the SQL database

data Group = Group {
     _people :: Map Integer Person
         }
 deriving (Eq)


-- | A wrapped representation of a Person
data Person = Person { _unPerson :: String}
  deriving (Eq)

instance Arbitrary Person where
  arbitrary = Person <$> arbitrary

-- | An Isomorphism between the representation that is pleasent to use in haskell
-- and the one that makes sense to store i.e. 'PersistEntity' 
personMapConverter :: Converter (Map Integer Person) [(Int64,String)]
personMapConverter = mapConverter `composeConverter` fmapConverter (bicomposeConverter integerConverter personConverter)

-- | This converter is embedded in 'personMapConverter'
personConverter :: Converter Person String
personConverter = (_unPerson,Person)


-- | A declaration for group.
mkPersist defaultCodegenConfig [groundhog|
- entity: Group
  constructors:
  - name: Group
    fields:
      - name: _people
        dbName: people
        exprName: MappedIdToPerson
        converter: personMapConverter
- primitive: Person
  converter: personConverter


|]

How to run tests

cabal configure --enable-tests && cabal build && cabal test

Changes

Revision history for groundhog-converters

0.0.0 -- YYYY-mm-dd

  • First version. Released on an unsuspecting world.
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