Text.JSON.FromJSValue

Interface for extracting data from JSValue.

Basic Parsing

class FromJSValue a where

Structures that can be parsed from JSON. Instances must declare either fromJSValue (parse directly from JSValue) or fromJSValueM (uses MonadReader)

Methods

fromJSValue :: JSValue -> Maybe a

fromJSValueM :: (JSValueContainer c, MonadReader c m) => m (Maybe a)

Instances

FromJSValue Bool

FromJSValue Int

FromJSValue Integer

FromJSValue String

FromJSValue ByteString

FromJSValue JSValue

FromJSValue a => FromJSValue [a]

FromJSValue a => FromJSValue (Maybe a)

(FromJSValue a, FromJSValue b) => FromJSValue (a, b)

Data Extraction

jsValueField :: (JSValueContainer c, MonadReader c m, FromJSValue a) => String -> m (Maybe (Maybe a))

Reading the value that is on some field. Returns Nothing if JSON is not an object or field is present but cannot be parsed, 'Just Nothing' if absent, and 'Just (Just a)' otherwise

fromJSValueField :: (JSValueContainer c, MonadReader c m, FromJSValue a) => String -> m (Maybe a)

Reading the value that is on some field. With field if current JSON is not object

fromJSValueFieldBase64 :: (JSValueContainer c, MonadReader c m) => String -> m (Maybe ByteString)

Version of fromJSValueField for Base64 encoded data to avoid memory leak.

fromJSValueFieldCustom :: (JSValueContainer c, MonadReader c m) => String -> m (Maybe a) -> m (Maybe a)

Generalization of fromJSValueField. Does not use FromJSValue instances

fromJSValueCustomMany :: (JSValueContainer c, MonadReader c m) => m (Maybe a) -> m (Maybe [a])

Runs parser on each element of underlaying json. Returns Just iff JSON is array.

fromJSValueCustomList :: (JSValueContainer c, MonadReader c m) => [m (Maybe a)] -> m (Maybe [a])

Generalization of fromJSValueCustomMany, where each element of array can have different parser.

Running

withJSValue :: Monad m => JSValue -> ReaderT JSValue m a -> m a

Simple runner