cb552f9 · typeable/postgresql-simple

git.iko.soy/typeable/postgresql-simple

Add the toJSONField and fromJSONField functions

These can be used as the default implementations for the toField and fromField methods for Haskell types that have a JSON representation in PostgreSQL.

commitcb552f96c740a002117619e3d4c05f51313a1d8d authorBas van Dijk <v.dijk.bas@gmail.com> dateThu 12 Sep 2013, 00:49 (13 years ago) parent63a00b2

2 files changed+29

compare with master

unifiedsplit

src/Database/PostgreSQL/Simple/FromField.hs+19 src/Database/PostgreSQL/Simple/ToField.hs+10

src/Database/PostgreSQL/Simple/FromField.hs+19

@@ -87,6 +87,8 @@ module Database.PostgreSQL.Simple.FromField

8787 , typeOid

8888 , PQ.Oid(..)

8989 , PQ.Format(..)

90+

91+ , fromJSONField

9092 ) where

9193

9294#include "MachDeps.h"

@@ -453,6 +455,23 @@ instance FromField JSON.Value where

453455 Left err -> returnError ConversionFailed f err

454456 Right val -> pure val

455457

458+-- | Parse a field to a JSON 'JSON.Value' and convert that into a

459+-- Haskell value using 'JSON.fromJSON'.

460+--

461+-- This can be used as the default implementation for the 'fromField'

462+-- method for Haskell types that have a JSON representation in

463+-- PostgreSQL.

464+--

465+-- The 'Typeable' constraint is required to show more informative

466+-- error messages when parsing fails.

467+fromJSONField :: (JSON.FromJSON a, Typeable a) => FieldParser a

468+fromJSONField f mbBs = do

469+ value <- fromField f mbBs

470+ case JSON.fromJSON value of

471+ JSON.Error err -> returnError ConversionFailed f $

472+ "JSON decoding error: " ++ err

473+ JSON.Success x -> pure x

474+

456475type Compat = PQ.Oid -> Bool

457476

458477okText, okText', okBinary, ok16, ok32, ok64, okInt :: Compat

src/Database/PostgreSQL/Simple/ToField.hs+10

@@ -18,6 +18,7 @@ module Database.PostgreSQL.Simple.ToField

1818 (

1919 Action(..)

2020 , ToField(..)

21+ , toJSONField

2122 , inQuotes

2223 ) where

2324

@@ -234,6 +235,15 @@ instance (ToField a) => ToField (Vector a) where

234235instance ToField JSON.Value where

235236 toField = toField . JSON.encode

236237

238+-- | Convert a Haskell value to a JSON 'JSON.Value' using

239+-- 'JSON.toJSON' and convert that to a field using 'toField'.

240+--

241+-- This can be used as the default implementation for the 'toField'

242+-- method for Haskell types that have a JSON representation in

243+-- PostgreSQL.

244+toJSONField :: JSON.ToJSON a => a -> Action

245+toJSONField = toField . JSON.toJSON

246+

237247-- | Surround a string with single-quote characters: \"@'@\"

238248--

239249-- This function /does not/ perform any other escaping.