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Add a combinator for decoding maybe fields #17

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Merged
merged 1 commit into from
Aug 5, 2016
Merged

Add a combinator for decoding maybe fields #17

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13 changes: 12 additions & 1 deletion src/Data/Argonaut/Decode/Combinators.purs
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Original file line number Diff line number Diff line change
Expand Up @@ -5,7 +5,7 @@ import Prelude
import Data.Argonaut.Core (JObject)
import Data.Argonaut.Decode.Class (class DecodeJson, decodeJson)
import Data.Either (Either(..))
import Data.Maybe (maybe)
import Data.Maybe (Maybe(Just, Nothing), maybe)
import Data.StrMap as SM

getField :: forall a. DecodeJson a => JObject -> String -> Either String a
Expand All @@ -16,3 +16,14 @@ getField o s =
(SM.lookup s o)

infix 7 getField as .?

getFieldOptional :: forall a. DecodeJson a => JObject -> String -> Either String (Maybe a)
getFieldOptional o s =
maybe
(pure Nothing)
decode
(SM.lookup s o)
where
decode json = Just <$> decodeJson json

infix 7 getFieldOptional as .??
3 changes: 3 additions & 0 deletions test/Test/Main.purs
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Expand Up @@ -143,6 +143,7 @@ data User
| Guest String
| Registered
{ name :: String
, bio :: Maybe String
, age :: Int
, balance :: Number
, banned :: Boolean
Expand All @@ -169,6 +170,7 @@ genericsCheck = do
logShow $ gEncodeJson $ Guest "guest's handle"
logShow $ gEncodeJson $ Registered
{ name: "user1"
, bio: Just "Ordinary User"
, age: 5
, balance: 26.6
, banned: false
Expand All @@ -178,6 +180,7 @@ genericsCheck = do
, Guest "someGuest"
, Registered
{ name: "user2"
, bio: Nothing
, age: 6
, balance: 32.1
, banned: false
Expand Down