json encoding example

encoding.hs

#!/usr/bin/env runhaskell
{-# LANGUAGE DeriveAnyClass    #-}
{-# LANGUAGE DeriveGeneric     #-}
{-# LANGUAGE OverloadedStrings #-}

import qualified Data.Aeson as Aeson
import Data.Text
import Data.Time.Clock
import GHC.Generics

data UserEvent = UserEvent
  { uuid      :: Text
  , eventName :: Text
  , timestamp :: UTCTime
  } deriving (Show, Eq, Generic, Aeson.ToJSON, Aeson.FromJSON)

main = do
  now <- getCurrentTime
  let ue = UserEvent "123-sadf-34" "whatever" now

  print (Aeson.encode ue)
  
--  stack runghc encoding.hs  
-- "{\"uuid\":\"123-sadf-34\",\"eventName\":\"whatever\",\"timestamp\":\"2016-06-18T21:06:57.184643000000Z\"}"