simpleAeson.hs

--{"message": "test",
-- "results": {"k":"value"}
--}


-- Simple Nested JSON Parse with Aeson 
{-# LANGUAGE OverloadedStrings #-}
import           Control.Applicative  ((<$>), (<*>))
import           Control.Lens
import           Control.Monad        (mzero)
import           Data.Aeson
import           Data.ByteString.Lazy as LBS
import qualified Data.Map             as M
import           Data.Monoid          ((<>))
import qualified Data.Text            as T
import           Network.Wreq

data Message = Message {
    v1 :: !T.Text
    , v2 :: !T.Text
} deriving (Show)

instance FromJSON Message where
    parseJSON (Object o) =
        Message <$> (o .: "message")
                <*> ((o .: "results") >>= (.:"k"))

    parseJSON _ = mzero

-- in Prelude 
r <- BS.readFile "p.json" 
let m = decode r :: Maybe Message