Article.hs

{-# LANGUAGE OverloadedStrings #-}
module Article where
import Data.Text.Lazy
import Data.Text.Lazy.Encoding
import Data.Aeson
import Control.Applicative
 
-- Define the Article constructor
-- e.g. Article 12 "some title" "some body text"
data Article = Article Integer Text Text -- id title bodyText
     deriving (Show)
 
 
-- Tell Aeson how to create an Article object from JSON string.
instance FromJSON Article where
     parseJSON (Object v) = Article <$>
                            v .:? "id" .!= 0 <*> -- the field "id" is optional
                            v .:  "title"    <*>
                            v .:  "bodyText"
 
 
-- Tell Aeson how to convert an Article object to a JSON string.
instance ToJSON Article where
     toJSON (Article id title bodyText) =
         object ["id" .= id,
                 "title" .= title,
                 "bodyText" .= bodyText]