Если у меня есть собственный тип данных для разбора JSON с помощью Aeson
data Response = Response
{ response :: [Body]
} deriving (Show)
instance FromJSON Response where
parseJSON (Object v) = Response <$> v .: "response"
parseJSON _ = mzero
data Body = Body
{ body_id :: Int
, brandId :: Int
} deriving (Show)
instance FromJSON Body where
parseJSON (Object v) = Body
<$> v .: "id"
<*> v .: "brandId"
parseJSON _ = mzero
raw :: BS.ByteString
raw = "{\"response\":[{\"id\":5977,\"brandId\":87}]}"
давая:
λ> decode raw :: Maybe Response
Just (Response {response = [Body {body_id = 5977, brandId = 87}]})
Как автоматически получить экземпляры для FromJSON
?
Я пытался:
data Response = Response
{ response :: [Body]
} deriving (Show,Generic)
data Body = Body
{ body_id :: Int
, brandId :: Int
} deriving (Show,Generic)
instance FromJSON Response
instance FromJSON Body
как было предложено в некоторых учебниках, но это дает:
λ> :l response.hs
[1 of 1] Compiling Response ( response.hs, interpreted )
response.hs:19:22:
Can't make a derived instance of `Generic Response':
You need DeriveGeneric to derive an instance for this class
In the data declaration for `Response'
response.hs:24:22:
Can't make a derived instance of `Generic Body':
You need DeriveGeneric to derive an instance for this class
In the data declaration for `Body'
Failed, modules loaded: none.
Что я делаю неправильно?