Re: [Haskell-cafe] JSON querying

On 02/17/2013 04:01 PM, Sergey Mironov wrote:

Hi folks. Hackage contains several JSON packages but as far as I see, they all provide 'static' conversion from JSON format to Haskell data type. Is there a method of converting object containing optional filed 'a' to for example Maybe a.

Data.Aeson does this with the .:? operator: instance FromJSON Bar where parseJSON (Object v) = Bar <$> v .: "required" <*> v .:? "optional"