practice: Test Data.Aeson

test_aeson.hs

{-# LANGUAGE OverloadedStrings #-}

import qualified System.IO.UTF8 as U
import Control.Applicative ((<$>), (<*>))
import Control.Monad (mzero)
import Data.Aeson
import Data.Aeson.Types
import Data.Text (Text)
import qualified Data.Attoparsec as AP (Result(..), parseOnly)

data Status = Status { text :: Text
                     , createdAt :: String
                     , user :: User
                     } deriving (Show)

data User = User { screenName :: String
                 } deriving (Show)

instance FromJSON Status where
  parseJSON (Object v) = Status
                          <$> v .: "text"
                          <*> v .: "created_at"
                          <*> v .: "user"
  parseJSON _          = mzero

instance FromJSON User where
  parseJSON (Object v) = User
                          <$> v .: "screen_name"
  parseJSON _          = mzero

main :: IO ()
main = do
  let p = AP.parseOnly json "{\"text\":\"ほげほげ\",\"created_at\":\"2012/05/20\",\"user\":{\"screen_name\":\"krdlab\"}}"
  case p of
    --Right j -> L.putStrLn $ encode j
    Right j -> U.putStrLn $ show $ (fromJSON j :: Result Status) -- 日本語が化ける...
    Left  m -> U.putStrLn $ "parse error: " ++ m