Enum

hasql.cabal

@@ -68,7 +68,7 @@ library
     -- parsing:
     attoparsec >= 0.10 && < 0.14,
     -- database:
-    postgresql-binary >= 0.7.2 && < 0.8,
+    postgresql-binary >= 0.7.3 && < 0.8,
     postgresql-libpq == 0.9.*,
     -- data:
     dlist >= 0.7 && < 0.8,

library/Hasql/Deserialization.hs

@@ -45,6 +45,7 @@ module Hasql.Deserialization
   array,
   composite,
   hstore,
+  enum,
   -- * Array
   Array,
   arrayDimension,
@@ -525,6 +526,13 @@ hstore :: (forall m. Monad m => Int -> m (Text, Maybe Text) -> m a) -> Value a
 hstore replicateM =
   Value (Value.decoder (const (Decoder.hstore replicateM Decoder.text_strict Decoder.text_strict)))
 
+-- |
+-- Given a partial mapping from text to value,
+-- produces a deserializer of that value.
+enum :: (Text -> Maybe a) -> Value a
+enum mapping =
+  Value (Value.decoder (const (Decoder.enum mapping)))
+
 
 -- ** Instances
 -------------------------

library/Hasql/Serialization.hs

@@ -25,6 +25,7 @@ module Hasql.Serialization
   uuid,
   json,
   array,
+  enum,
   -- * Array
   Array,
   arrayValue,
@@ -220,6 +221,15 @@ array (Array imp) =
   Array.run imp & \(arrayOID, encoder') ->
     Value (Value.Value arrayOID arrayOID encoder')
 
+-- |
+-- Given a function,
+-- which maps the value into the textual enum label from the DB side,
+-- produces a serializer of that value.
+{-# INLINABLE enum #-}
+enum :: (a -> Text) -> Value a
+enum mapping =
+  Value (Value.unsafePTI PTI.text (const (Encoder.enum mapping)))
+
 
 -- ** Instances
 -------------------------