src/Rel8/Type/JSONEncoded.hs · rel8

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rel8/src/Rel8/Type/JSONEncoded.hs

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1module Rel8.Type.JSONEncoded ( JSONEncoded(..) ) where

3-- aeson

4import Data.Aeson ( FromJSON, ToJSON, parseJSON, toJSON )

5import Data.Aeson.Types ( parseEither )

7-- base

8import Prelude

10-- rel8

11import Rel8.Type ( DBType(..) )

12import Rel8.Type.Information ( parseTypeInformation )

15-- | A deriving-via helper type for column types that store a Haskell value

16-- using a JSON encoding described by @aeson@'s 'ToJSON' and 'FromJSON' type

17-- classes.

18--

19-- The declaration:

20--

21-- >>> import Data.Aeson

22--

23-- >>> :{

24-- data Pet = Pet { petName :: String, petAge :: Int }

25-- deriving (Generic, ToJSON, FromJSON)

26-- deriving PrimitiveType via JSONEncoded Pet

27-- :}

28--

29-- will allow you to store @Pet@ values in a single SQL column (stored as

30-- @json@ values).

31newtype JSONEncoded a = JSONEncoded { fromJSONEncoded :: a }

34instance (FromJSON a, ToJSON a) => DBType (JSONEncoded a) where

35 typeInformation = parseTypeInformation f g typeInformation

36 where

37 f = fmap JSONEncoded . parseEither parseJSON

38 g = toJSON . fromJSONEncoded