Safe Haskell	None
Language	Haskell2010

Prolude.Json

Synopsis

eitherDecode :: FromJSON a => ByteString -> Either String a
encode :: ToJSON a => a -> ByteString
class ToJSON a
withText :: String -> (Text -> Parser a) -> Value -> Parser a
withObject :: String -> (Object -> Parser a) -> Value -> Parser a
class FromJSON a
data Parser a
jsonEitherDecode :: FromJSON a => ByteString -> Either String a
jsonEncode :: ToJSON a => a -> ByteString

Documentation

eitherDecode :: FromJSON a => ByteString -> Either String a #

Like decode but returns an error message when decoding fails.

encode :: ToJSON a => a -> ByteString #

Efficiently serialize a JSON value as a lazy ByteString.

This is implemented in terms of the ToJSON class's toEncoding method.

class ToJSON a #

A type that can be converted to JSON.

Instances in general must specify toJSON and should (but don't need to) specify toEncoding.

An example type and instance:

-- Allow ourselves to write Text literals.
{-# LANGUAGE OverloadedStrings #-}

data Coord = Coord { x :: Double, y :: Double }

instance ToJSON Coord where
  toJSON (Coord x y) = object ["x" .= x, "y" .= y]

  toEncoding (Coord x y) = pairs ("x" .= x <> "y" .= y)

Instead of manually writing your ToJSON instance, there are two options to do it automatically:

Data.Aeson.TH provides Template Haskell functions which will derive an instance at compile time. The generated instance is optimized for your type so it will probably be more efficient than the following option.
The compiler can provide a default generic implementation for toJSON.

To use the second, simply add a deriving Generic clause to your datatype and declare a ToJSON instance. If you require nothing other than defaultOptions, it is sufficient to write (and this is the only alternative where the default toJSON implementation is sufficient):

{-# LANGUAGE DeriveGeneric #-}

import GHC.Generics

data Coord = Coord { x :: Double, y :: Double } deriving Generic

instance ToJSON Coord where
    toEncoding = genericToEncoding defaultOptions

If on the other hand you wish to customize the generic decoding, you have to implement both methods:

customOptions = defaultOptions
                { fieldLabelModifier = map toUpper
                }

instance ToJSON Coord where
    toJSON     = genericToJSON customOptions
    toEncoding = genericToEncoding customOptions

Previous versions of this library only had the toJSON method. Adding toEncoding had two reasons:

toEncoding is more efficient for the common case that the output of toJSON is directly serialized to a ByteString. Further, expressing either method in terms of the other would be non-optimal.
The choice of defaults allows a smooth transition for existing users: Existing instances that do not define toEncoding still compile and have the correct semantics. This is ensured by making the default implementation of toEncoding use toJSON. This produces correct results, but since it performs an intermediate conversion to a Value, it will be less efficient than directly emitting an Encoding. (this also means that specifying nothing more than instance ToJSON Coord would be sufficient as a generically decoding instance, but there probably exists no good reason to not specify toEncoding in new instances.)

Instances

Instances details

ToJSON Bool
Instance details Defined in Data.Aeson.Types.ToJSON Methods toJSON :: Bool -> Value # toEncoding :: Bool -> Encoding # toJSONList :: [Bool] -> Value # toEncodingList :: [Bool] -> Encoding #
ToJSON Char
Instance details Defined in Data.Aeson.Types.ToJSON Methods toJSON :: Char -> Value # toEncoding :: Char -> Encoding # toJSONList :: [Char] -> Value # toEncodingList :: [Char] -> Encoding #
ToJSON Double
Instance details Defined in Data.Aeson.Types.ToJSON Methods toJSON :: Double -> Value # toEncoding :: Double -> Encoding # toJSONList :: [Double] -> Value # toEncodingList :: [Double] -> Encoding #
ToJSON Float
Instance details Defined in Data.Aeson.Types.ToJSON Methods toJSON :: Float -> Value # toEncoding :: Float -> Encoding # toJSONList :: [Float] -> Value # toEncodingList :: [Float] -> Encoding #
ToJSON Int
Instance details Defined in Data.Aeson.Types.ToJSON Methods toJSON :: Int -> Value # toEncoding :: Int -> Encoding # toJSONList :: [Int] -> Value # toEncodingList :: [Int] -> Encoding #
ToJSON Int8
Instance details Defined in Data.Aeson.Types.ToJSON Methods toJSON :: Int8 -> Value # toEncoding :: Int8 -> Encoding # toJSONList :: [Int8] -> Value # toEncodingList :: [Int8] -> Encoding #
ToJSON Int16
Instance details Defined in Data.Aeson.Types.ToJSON Methods toJSON :: Int16 -> Value # toEncoding :: Int16 -> Encoding # toJSONList :: [Int16] -> Value # toEncodingList :: [Int16] -> Encoding #
ToJSON Int32
Instance details Defined in Data.Aeson.Types.ToJSON Methods toJSON :: Int32 -> Value # toEncoding :: Int32 -> Encoding # toJSONList :: [Int32] -> Value # toEncodingList :: [Int32] -> Encoding #
ToJSON Int64
Instance details Defined in Data.Aeson.Types.ToJSON Methods toJSON :: Int64 -> Value # toEncoding :: Int64 -> Encoding # toJSONList :: [Int64] -> Value # toEncodingList :: [Int64] -> Encoding #
ToJSON Integer
Instance details Defined in Data.Aeson.Types.ToJSON Methods toJSON :: Integer -> Value # toEncoding :: Integer -> Encoding # toJSONList :: [Integer] -> Value # toEncodingList :: [Integer] -> Encoding #
ToJSON Natural
Instance details Defined in Data.Aeson.Types.ToJSON Methods toJSON :: Natural -> Value # toEncoding :: Natural -> Encoding # toJSONList :: [Natural] -> Value # toEncodingList :: [Natural] -> Encoding #
ToJSON Ordering
Instance details Defined in Data.Aeson.Types.ToJSON Methods toJSON :: Ordering -> Value # toEncoding :: Ordering -> Encoding # toJSONList :: [Ordering] -> Value # toEncodingList :: [Ordering] -> Encoding #
ToJSON Word
Instance details Defined in Data.Aeson.Types.ToJSON Methods toJSON :: Word -> Value # toEncoding :: Word -> Encoding # toJSONList :: [Word] -> Value # toEncodingList :: [Word] -> Encoding #
ToJSON Word8
Instance details Defined in Data.Aeson.Types.ToJSON Methods toJSON :: Word8 -> Value # toEncoding :: Word8 -> Encoding # toJSONList :: [Word8] -> Value # toEncodingList :: [Word8] -> Encoding #
ToJSON Word16
Instance details Defined in Data.Aeson.Types.ToJSON Methods toJSON :: Word16 -> Value # toEncoding :: Word16 -> Encoding # toJSONList :: [Word16] -> Value # toEncodingList :: [Word16] -> Encoding #
ToJSON Word32
Instance details Defined in Data.Aeson.Types.ToJSON Methods toJSON :: Word32 -> Value # toEncoding :: Word32 -> Encoding # toJSONList :: [Word32] -> Value # toEncodingList :: [Word32] -> Encoding #
ToJSON Word64
Instance details Defined in Data.Aeson.Types.ToJSON Methods toJSON :: Word64 -> Value # toEncoding :: Word64 -> Encoding # toJSONList :: [Word64] -> Value # toEncodingList :: [Word64] -> Encoding #
ToJSON ()
Instance details Defined in Data.Aeson.Types.ToJSON Methods toJSON :: () -> Value # toEncoding :: () -> Encoding # toJSONList :: [()] -> Value # toEncodingList :: [()] -> Encoding #
ToJSON Version
Instance details Defined in Data.Aeson.Types.ToJSON Methods toJSON :: Version -> Value # toEncoding :: Version -> Encoding # toJSONList :: [Version] -> Value # toEncodingList :: [Version] -> Encoding #
ToJSON Scientific
Instance details Defined in Data.Aeson.Types.ToJSON Methods toJSON :: Scientific -> Value # toEncoding :: Scientific -> Encoding # toJSONList :: [Scientific] -> Value # toEncodingList :: [Scientific] -> Encoding #
ToJSON Text
Instance details Defined in Data.Aeson.Types.ToJSON Methods toJSON :: Text -> Value # toEncoding :: Text -> Encoding # toJSONList :: [Text] -> Value # toEncodingList :: [Text] -> Encoding #
ToJSON UTCTime
Instance details Defined in Data.Aeson.Types.ToJSON Methods toJSON :: UTCTime -> Value # toEncoding :: UTCTime -> Encoding # toJSONList :: [UTCTime] -> Value # toEncodingList :: [UTCTime] -> Encoding #
ToJSON Value
Instance details Defined in Data.Aeson.Types.ToJSON Methods toJSON :: Value -> Value # toEncoding :: Value -> Encoding # toJSONList :: [Value] -> Value # toEncodingList :: [Value] -> Encoding #
ToJSON DotNetTime
Instance details Defined in Data.Aeson.Types.ToJSON Methods toJSON :: DotNetTime -> Value # toEncoding :: DotNetTime -> Encoding # toJSONList :: [DotNetTime] -> Value # toEncodingList :: [DotNetTime] -> Encoding #
ToJSON Text
Instance details Defined in Data.Aeson.Types.ToJSON Methods toJSON :: Text -> Value # toEncoding :: Text -> Encoding # toJSONList :: [Text] -> Value # toEncodingList :: [Text] -> Encoding #
ToJSON Number
Instance details Defined in Data.Aeson.Types.ToJSON Methods toJSON :: Number -> Value # toEncoding :: Number -> Encoding # toJSONList :: [Number] -> Value # toEncodingList :: [Number] -> Encoding #
ToJSON Void
Instance details Defined in Data.Aeson.Types.ToJSON Methods toJSON :: Void -> Value # toEncoding :: Void -> Encoding # toJSONList :: [Void] -> Value # toEncodingList :: [Void] -> Encoding #
ToJSON CTime
Instance details Defined in Data.Aeson.Types.ToJSON Methods toJSON :: CTime -> Value # toEncoding :: CTime -> Encoding # toJSONList :: [CTime] -> Value # toEncodingList :: [CTime] -> Encoding #
ToJSON IntSet
Instance details Defined in Data.Aeson.Types.ToJSON Methods toJSON :: IntSet -> Value # toEncoding :: IntSet -> Encoding # toJSONList :: [IntSet] -> Value # toEncodingList :: [IntSet] -> Encoding #
ToJSON PersistValue
Instance details Defined in Database.Persist.Types.Base Methods toJSON :: PersistValue -> Value # toEncoding :: PersistValue -> Encoding # toJSONList :: [PersistValue] -> Value # toEncodingList :: [PersistValue] -> Encoding #
ToJSON Swagger
Instance details Defined in Data.Swagger.Internal Methods toJSON :: Swagger -> Value # toEncoding :: Swagger -> Encoding # toJSONList :: [Swagger] -> Value # toEncodingList :: [Swagger] -> Encoding #
ToJSON Info
Instance details Defined in Data.Swagger.Internal Methods toJSON :: Info -> Value # toEncoding :: Info -> Encoding # toJSONList :: [Info] -> Value # toEncodingList :: [Info] -> Encoding #
ToJSON Contact
Instance details Defined in Data.Swagger.Internal Methods toJSON :: Contact -> Value # toEncoding :: Contact -> Encoding # toJSONList :: [Contact] -> Value # toEncodingList :: [Contact] -> Encoding #
ToJSON License
Instance details Defined in Data.Swagger.Internal Methods toJSON :: License -> Value # toEncoding :: License -> Encoding # toJSONList :: [License] -> Value # toEncodingList :: [License] -> Encoding #
ToJSON Host
Instance details Defined in Data.Swagger.Internal Methods toJSON :: Host -> Value # toEncoding :: Host -> Encoding # toJSONList :: [Host] -> Value # toEncodingList :: [Host] -> Encoding #
ToJSON Scheme
Instance details Defined in Data.Swagger.Internal Methods toJSON :: Scheme -> Value # toEncoding :: Scheme -> Encoding # toJSONList :: [Scheme] -> Value # toEncodingList :: [Scheme] -> Encoding #
ToJSON PathItem
Instance details Defined in Data.Swagger.Internal Methods toJSON :: PathItem -> Value # toEncoding :: PathItem -> Encoding # toJSONList :: [PathItem] -> Value # toEncodingList :: [PathItem] -> Encoding #
ToJSON Operation
Instance details Defined in Data.Swagger.Internal Methods toJSON :: Operation -> Value # toEncoding :: Operation -> Encoding # toJSONList :: [Operation] -> Value # toEncodingList :: [Operation] -> Encoding #
ToJSON MimeList
Instance details Defined in Data.Swagger.Internal Methods toJSON :: MimeList -> Value # toEncoding :: MimeList -> Encoding # toJSONList :: [MimeList] -> Value # toEncodingList :: [MimeList] -> Encoding #
ToJSON Param
Instance details Defined in Data.Swagger.Internal Methods toJSON :: Param -> Value # toEncoding :: Param -> Encoding # toJSONList :: [Param] -> Value # toEncodingList :: [Param] -> Encoding #
ToJSON ParamAnySchema
Instance details Defined in Data.Swagger.Internal Methods toJSON :: ParamAnySchema -> Value # toEncoding :: ParamAnySchema -> Encoding # toJSONList :: [ParamAnySchema] -> Value # toEncodingList :: [ParamAnySchema] -> Encoding #
ToJSON ParamOtherSchema
Instance details Defined in Data.Swagger.Internal Methods toJSON :: ParamOtherSchema -> Value # toEncoding :: ParamOtherSchema -> Encoding # toJSONList :: [ParamOtherSchema] -> Value # toEncodingList :: [ParamOtherSchema] -> Encoding #
ToJSON ParamLocation
Instance details Defined in Data.Swagger.Internal Methods toJSON :: ParamLocation -> Value # toEncoding :: ParamLocation -> Encoding # toJSONList :: [ParamLocation] -> Value # toEncodingList :: [ParamLocation] -> Encoding #
ToJSON Schema
Instance details Defined in Data.Swagger.Internal Methods toJSON :: Schema -> Value # toEncoding :: Schema -> Encoding # toJSONList :: [Schema] -> Value # toEncodingList :: [Schema] -> Encoding #
ToJSON Xml
Instance details Defined in Data.Swagger.Internal Methods toJSON :: Xml -> Value # toEncoding :: Xml -> Encoding # toJSONList :: [Xml] -> Value # toEncodingList :: [Xml] -> Encoding #
ToJSON Responses
Instance details Defined in Data.Swagger.Internal Methods toJSON :: Responses -> Value # toEncoding :: Responses -> Encoding # toJSONList :: [Responses] -> Value # toEncodingList :: [Responses] -> Encoding #
ToJSON Response
Instance details Defined in Data.Swagger.Internal Methods toJSON :: Response -> Value # toEncoding :: Response -> Encoding # toJSONList :: [Response] -> Value # toEncodingList :: [Response] -> Encoding #
ToJSON Header
Instance details Defined in Data.Swagger.Internal Methods toJSON :: Header -> Value # toEncoding :: Header -> Encoding # toJSONList :: [Header] -> Value # toEncodingList :: [Header] -> Encoding #
ToJSON Example
Instance details Defined in Data.Swagger.Internal Methods toJSON :: Example -> Value # toEncoding :: Example -> Encoding # toJSONList :: [Example] -> Value # toEncodingList :: [Example] -> Encoding #
ToJSON ApiKeyLocation
Instance details Defined in Data.Swagger.Internal Methods toJSON :: ApiKeyLocation -> Value # toEncoding :: ApiKeyLocation -> Encoding # toJSONList :: [ApiKeyLocation] -> Value # toEncodingList :: [ApiKeyLocation] -> Encoding #
ToJSON ApiKeyParams
Instance details Defined in Data.Swagger.Internal Methods toJSON :: ApiKeyParams -> Value # toEncoding :: ApiKeyParams -> Encoding # toJSONList :: [ApiKeyParams] -> Value # toEncodingList :: [ApiKeyParams] -> Encoding #
ToJSON OAuth2Flow
Instance details Defined in Data.Swagger.Internal Methods toJSON :: OAuth2Flow -> Value # toEncoding :: OAuth2Flow -> Encoding # toJSONList :: [OAuth2Flow] -> Value # toEncodingList :: [OAuth2Flow] -> Encoding #
ToJSON OAuth2Params
Instance details Defined in Data.Swagger.Internal Methods toJSON :: OAuth2Params -> Value # toEncoding :: OAuth2Params -> Encoding # toJSONList :: [OAuth2Params] -> Value # toEncodingList :: [OAuth2Params] -> Encoding #
ToJSON SecuritySchemeType
Instance details Defined in Data.Swagger.Internal Methods toJSON :: SecuritySchemeType -> Value # toEncoding :: SecuritySchemeType -> Encoding # toJSONList :: [SecuritySchemeType] -> Value # toEncodingList :: [SecuritySchemeType] -> Encoding #
ToJSON SecurityScheme
Instance details Defined in Data.Swagger.Internal Methods toJSON :: SecurityScheme -> Value # toEncoding :: SecurityScheme -> Encoding # toJSONList :: [SecurityScheme] -> Value # toEncodingList :: [SecurityScheme] -> Encoding #
ToJSON SecurityDefinitions
Instance details Defined in Data.Swagger.Internal Methods toJSON :: SecurityDefinitions -> Value # toEncoding :: SecurityDefinitions -> Encoding # toJSONList :: [SecurityDefinitions] -> Value # toEncodingList :: [SecurityDefinitions] -> Encoding #
ToJSON SecurityRequirement
Instance details Defined in Data.Swagger.Internal Methods toJSON :: SecurityRequirement -> Value # toEncoding :: SecurityRequirement -> Encoding # toJSONList :: [SecurityRequirement] -> Value # toEncodingList :: [SecurityRequirement] -> Encoding #
ToJSON Tag
Instance details Defined in Data.Swagger.Internal Methods toJSON :: Tag -> Value # toEncoding :: Tag -> Encoding # toJSONList :: [Tag] -> Value # toEncodingList :: [Tag] -> Encoding #
ToJSON ExternalDocs
Instance details Defined in Data.Swagger.Internal Methods toJSON :: ExternalDocs -> Value # toEncoding :: ExternalDocs -> Encoding # toJSONList :: [ExternalDocs] -> Value # toEncodingList :: [ExternalDocs] -> Encoding #
ToJSON Reference
Instance details Defined in Data.Swagger.Internal Methods toJSON :: Reference -> Value # toEncoding :: Reference -> Encoding # toJSONList :: [Reference] -> Value # toEncodingList :: [Reference] -> Encoding #
ToJSON URL
Instance details Defined in Data.Swagger.Internal Methods toJSON :: URL -> Value # toEncoding :: URL -> Encoding # toJSONList :: [URL] -> Value # toEncodingList :: [URL] -> Encoding #
ToJSON AdditionalProperties
Instance details Defined in Data.Swagger.Internal Methods toJSON :: AdditionalProperties -> Value # toEncoding :: AdditionalProperties -> Encoding # toJSONList :: [AdditionalProperties] -> Value # toEncodingList :: [AdditionalProperties] -> Encoding #
ToJSON ZonedTime
Instance details Defined in Data.Aeson.Types.ToJSON Methods toJSON :: ZonedTime -> Value # toEncoding :: ZonedTime -> Encoding # toJSONList :: [ZonedTime] -> Value # toEncodingList :: [ZonedTime] -> Encoding #
ToJSON LocalTime
Instance details Defined in Data.Aeson.Types.ToJSON Methods toJSON :: LocalTime -> Value # toEncoding :: LocalTime -> Encoding # toJSONList :: [LocalTime] -> Value # toEncodingList :: [LocalTime] -> Encoding #
ToJSON TimeOfDay
Instance details Defined in Data.Aeson.Types.ToJSON Methods toJSON :: TimeOfDay -> Value # toEncoding :: TimeOfDay -> Encoding # toJSONList :: [TimeOfDay] -> Value # toEncodingList :: [TimeOfDay] -> Encoding #
ToJSON CalendarDiffTime
Instance details Defined in Data.Aeson.Types.ToJSON Methods toJSON :: CalendarDiffTime -> Value # toEncoding :: CalendarDiffTime -> Encoding # toJSONList :: [CalendarDiffTime] -> Value # toEncodingList :: [CalendarDiffTime] -> Encoding #
ToJSON SystemTime	Encoded as number
Instance details Defined in Data.Aeson.Types.ToJSON Methods toJSON :: SystemTime -> Value # toEncoding :: SystemTime -> Encoding # toJSONList :: [SystemTime] -> Value # toEncodingList :: [SystemTime] -> Encoding #
ToJSON NominalDiffTime
Instance details Defined in Data.Aeson.Types.ToJSON Methods toJSON :: NominalDiffTime -> Value # toEncoding :: NominalDiffTime -> Encoding # toJSONList :: [NominalDiffTime] -> Value # toEncodingList :: [NominalDiffTime] -> Encoding #
ToJSON DiffTime
Instance details Defined in Data.Aeson.Types.ToJSON Methods toJSON :: DiffTime -> Value # toEncoding :: DiffTime -> Encoding # toJSONList :: [DiffTime] -> Value # toEncodingList :: [DiffTime] -> Encoding #
ToJSON DayOfWeek
Instance details Defined in Data.Aeson.Types.ToJSON Methods toJSON :: DayOfWeek -> Value # toEncoding :: DayOfWeek -> Encoding # toJSONList :: [DayOfWeek] -> Value # toEncodingList :: [DayOfWeek] -> Encoding #
ToJSON Day
Instance details Defined in Data.Aeson.Types.ToJSON Methods toJSON :: Day -> Value # toEncoding :: Day -> Encoding # toJSONList :: [Day] -> Value # toEncodingList :: [Day] -> Encoding #
ToJSON CalendarDiffDays
Instance details Defined in Data.Aeson.Types.ToJSON Methods toJSON :: CalendarDiffDays -> Value # toEncoding :: CalendarDiffDays -> Encoding # toJSONList :: [CalendarDiffDays] -> Value # toEncodingList :: [CalendarDiffDays] -> Encoding #
ToJSON UUID
Instance details Defined in Data.Aeson.Types.ToJSON Methods toJSON :: UUID -> Value # toEncoding :: UUID -> Encoding # toJSONList :: [UUID] -> Value # toEncodingList :: [UUID] -> Encoding #
ToJSON a => ToJSON [a]
Instance details Defined in Data.Aeson.Types.ToJSON Methods toJSON :: [a] -> Value # toEncoding :: [a] -> Encoding # toJSONList :: [[a]] -> Value # toEncodingList :: [[a]] -> Encoding #
ToJSON a => ToJSON (Maybe a)
Instance details Defined in Data.Aeson.Types.ToJSON Methods toJSON :: Maybe a -> Value # toEncoding :: Maybe a -> Encoding # toJSONList :: [Maybe a] -> Value # toEncodingList :: [Maybe a] -> Encoding #
(ToJSON a, Integral a) => ToJSON (Ratio a)
Instance details Defined in Data.Aeson.Types.ToJSON Methods toJSON :: Ratio a -> Value # toEncoding :: Ratio a -> Encoding # toJSONList :: [Ratio a] -> Value # toEncodingList :: [Ratio a] -> Encoding #
ToJSON a => ToJSON (Min a)
Instance details Defined in Data.Aeson.Types.ToJSON Methods toJSON :: Min a -> Value # toEncoding :: Min a -> Encoding # toJSONList :: [Min a] -> Value # toEncodingList :: [Min a] -> Encoding #
ToJSON a => ToJSON (Max a)
Instance details Defined in Data.Aeson.Types.ToJSON Methods toJSON :: Max a -> Value # toEncoding :: Max a -> Encoding # toJSONList :: [Max a] -> Value # toEncodingList :: [Max a] -> Encoding #
ToJSON a => ToJSON (First a)
Instance details Defined in Data.Aeson.Types.ToJSON Methods toJSON :: First a -> Value # toEncoding :: First a -> Encoding # toJSONList :: [First a] -> Value # toEncodingList :: [First a] -> Encoding #
ToJSON a => ToJSON (Last a)
Instance details Defined in Data.Aeson.Types.ToJSON Methods toJSON :: Last a -> Value # toEncoding :: Last a -> Encoding # toJSONList :: [Last a] -> Value # toEncodingList :: [Last a] -> Encoding #
ToJSON a => ToJSON (WrappedMonoid a)
Instance details Defined in Data.Aeson.Types.ToJSON Methods toJSON :: WrappedMonoid a -> Value # toEncoding :: WrappedMonoid a -> Encoding # toJSONList :: [WrappedMonoid a] -> Value # toEncodingList :: [WrappedMonoid a] -> Encoding #
ToJSON a => ToJSON (Option a)
Instance details Defined in Data.Aeson.Types.ToJSON Methods toJSON :: Option a -> Value # toEncoding :: Option a -> Encoding # toJSONList :: [Option a] -> Value # toEncodingList :: [Option a] -> Encoding #
ToJSON a => ToJSON (Identity a)
Instance details Defined in Data.Aeson.Types.ToJSON Methods toJSON :: Identity a -> Value # toEncoding :: Identity a -> Encoding # toJSONList :: [Identity a] -> Value # toEncodingList :: [Identity a] -> Encoding #
ToJSON a => ToJSON (First a)
Instance details Defined in Data.Aeson.Types.ToJSON Methods toJSON :: First a -> Value # toEncoding :: First a -> Encoding # toJSONList :: [First a] -> Value # toEncodingList :: [First a] -> Encoding #
ToJSON a => ToJSON (Last a)
Instance details Defined in Data.Aeson.Types.ToJSON Methods toJSON :: Last a -> Value # toEncoding :: Last a -> Encoding # toJSONList :: [Last a] -> Value # toEncodingList :: [Last a] -> Encoding #
ToJSON a => ToJSON (Dual a)
Instance details Defined in Data.Aeson.Types.ToJSON Methods toJSON :: Dual a -> Value # toEncoding :: Dual a -> Encoding # toJSONList :: [Dual a] -> Value # toEncodingList :: [Dual a] -> Encoding #
ToJSON a => ToJSON (NonEmpty a)
Instance details Defined in Data.Aeson.Types.ToJSON Methods toJSON :: NonEmpty a -> Value # toEncoding :: NonEmpty a -> Encoding # toJSONList :: [NonEmpty a] -> Value # toEncodingList :: [NonEmpty a] -> Encoding #
ToJSON a => ToJSON (IntMap a)
Instance details Defined in Data.Aeson.Types.ToJSON Methods toJSON :: IntMap a -> Value # toEncoding :: IntMap a -> Encoding # toJSONList :: [IntMap a] -> Value # toEncodingList :: [IntMap a] -> Encoding #
ToJSON v => ToJSON (Tree v)
Instance details Defined in Data.Aeson.Types.ToJSON Methods toJSON :: Tree v -> Value # toEncoding :: Tree v -> Encoding # toJSONList :: [Tree v] -> Value # toEncodingList :: [Tree v] -> Encoding #
ToJSON a => ToJSON (Seq a)
Instance details Defined in Data.Aeson.Types.ToJSON Methods toJSON :: Seq a -> Value # toEncoding :: Seq a -> Encoding # toJSONList :: [Seq a] -> Value # toEncodingList :: [Seq a] -> Encoding #
ToJSON a => ToJSON (Set a)
Instance details Defined in Data.Aeson.Types.ToJSON Methods toJSON :: Set a -> Value # toEncoding :: Set a -> Encoding # toJSONList :: [Set a] -> Value # toEncodingList :: [Set a] -> Encoding #
ToJSON1 f => ToJSON (Fix f)	Since: aeson-1.5.3.0
Instance details Defined in Data.Aeson.Types.ToJSON Methods toJSON :: Fix f -> Value # toEncoding :: Fix f -> Encoding # toJSONList :: [Fix f] -> Value # toEncodingList :: [Fix f] -> Encoding #
(ToJSON1 f, Functor f) => ToJSON (Mu f)	Since: aeson-1.5.3.0
Instance details Defined in Data.Aeson.Types.ToJSON Methods toJSON :: Mu f -> Value # toEncoding :: Mu f -> Encoding # toJSONList :: [Mu f] -> Value # toEncodingList :: [Mu f] -> Encoding #
(ToJSON1 f, Functor f) => ToJSON (Nu f)	Since: aeson-1.5.3.0
Instance details Defined in Data.Aeson.Types.ToJSON Methods toJSON :: Nu f -> Value # toEncoding :: Nu f -> Encoding # toJSONList :: [Nu f] -> Value # toEncodingList :: [Nu f] -> Encoding #
ToJSON a => ToJSON (DNonEmpty a)	Since: aeson-1.5.3.0
Instance details Defined in Data.Aeson.Types.ToJSON Methods toJSON :: DNonEmpty a -> Value # toEncoding :: DNonEmpty a -> Encoding # toJSONList :: [DNonEmpty a] -> Value # toEncodingList :: [DNonEmpty a] -> Encoding #
ToJSON a => ToJSON (DList a)
Instance details Defined in Data.Aeson.Types.ToJSON Methods toJSON :: DList a -> Value # toEncoding :: DList a -> Encoding # toJSONList :: [DList a] -> Value # toEncodingList :: [DList a] -> Encoding #
ToJSON a => ToJSON (HashSet a)
Instance details Defined in Data.Aeson.Types.ToJSON Methods toJSON :: HashSet a -> Value # toEncoding :: HashSet a -> Encoding # toJSONList :: [HashSet a] -> Value # toEncodingList :: [HashSet a] -> Encoding #
ToJSON a => ToJSON (InsOrdHashSet a)
Instance details Defined in Data.HashSet.InsOrd Methods toJSON :: InsOrdHashSet a -> Value # toEncoding :: InsOrdHashSet a -> Encoding # toJSONList :: [InsOrdHashSet a] -> Value # toEncodingList :: [InsOrdHashSet a] -> Encoding #
(Prim a, ToJSON a) => ToJSON (Vector a)
Instance details Defined in Data.Aeson.Types.ToJSON Methods toJSON :: Vector a -> Value # toEncoding :: Vector a -> Encoding # toJSONList :: [Vector a] -> Value # toEncodingList :: [Vector a] -> Encoding #
(Storable a, ToJSON a) => ToJSON (Vector a)
Instance details Defined in Data.Aeson.Types.ToJSON Methods toJSON :: Vector a -> Value # toEncoding :: Vector a -> Encoding # toJSONList :: [Vector a] -> Value # toEncodingList :: [Vector a] -> Encoding #
(Vector Vector a, ToJSON a) => ToJSON (Vector a)
Instance details Defined in Data.Aeson.Types.ToJSON Methods toJSON :: Vector a -> Value # toEncoding :: Vector a -> Encoding # toJSONList :: [Vector a] -> Value # toEncodingList :: [Vector a] -> Encoding #
ToJSON a => ToJSON (Vector a)
Instance details Defined in Data.Aeson.Types.ToJSON Methods toJSON :: Vector a -> Value # toEncoding :: Vector a -> Encoding # toJSONList :: [Vector a] -> Value # toEncodingList :: [Vector a] -> Encoding #
(Prim a, ToJSON a) => ToJSON (PrimArray a)
Instance details Defined in Data.Aeson.Types.ToJSON Methods toJSON :: PrimArray a -> Value # toEncoding :: PrimArray a -> Encoding # toJSONList :: [PrimArray a] -> Value # toEncodingList :: [PrimArray a] -> Encoding #
ToJSON a => ToJSON (SmallArray a)
Instance details Defined in Data.Aeson.Types.ToJSON Methods toJSON :: SmallArray a -> Value # toEncoding :: SmallArray a -> Encoding # toJSONList :: [SmallArray a] -> Value # toEncodingList :: [SmallArray a] -> Encoding #
ToJSON a => ToJSON (Array a)
Instance details Defined in Data.Aeson.Types.ToJSON Methods toJSON :: Array a -> Value # toEncoding :: Array a -> Encoding # toJSONList :: [Array a] -> Value # toEncodingList :: [Array a] -> Encoding #
ToJSON a => ToJSON (Maybe a)	Since: aeson-1.5.3.0
Instance details Defined in Data.Aeson.Types.ToJSON Methods toJSON :: Maybe a -> Value # toEncoding :: Maybe a -> Encoding # toJSONList :: [Maybe a] -> Value # toEncodingList :: [Maybe a] -> Encoding #
ToJSON (ParamSchema t) => ToJSON (SwaggerItems t)	As for nullary schema for 0-arity type constructors, see https://github.com/GetShopTV/swagger2/issues/167. `>>>` `encode (SwaggerItemsArray [])`"{\"example\":[],\"items\":{},\"maxItems\":0}"
Instance details Defined in Data.Swagger.Internal Methods toJSON :: SwaggerItems t -> Value # toEncoding :: SwaggerItems t -> Encoding # toJSONList :: [SwaggerItems t] -> Value # toEncodingList :: [SwaggerItems t] -> Encoding #
ToJSON (SwaggerType t)
Instance details Defined in Data.Swagger.Internal Methods toJSON :: SwaggerType t -> Value # toEncoding :: SwaggerType t -> Encoding # toJSONList :: [SwaggerType t] -> Value # toEncodingList :: [SwaggerType t] -> Encoding #
ToJSON (CollectionFormat t)
Instance details Defined in Data.Swagger.Internal Methods toJSON :: CollectionFormat t -> Value # toEncoding :: CollectionFormat t -> Encoding # toJSONList :: [CollectionFormat t] -> Value # toEncodingList :: [CollectionFormat t] -> Encoding #
ToJSON (ParamSchema k)
Instance details Defined in Data.Swagger.Internal Methods toJSON :: ParamSchema k -> Value # toEncoding :: ParamSchema k -> Encoding # toJSONList :: [ParamSchema k] -> Value # toEncodingList :: [ParamSchema k] -> Encoding #
ToJSON (Referenced Param)
Instance details Defined in Data.Swagger.Internal Methods toJSON :: Referenced Param -> Value # toEncoding :: Referenced Param -> Encoding # toJSONList :: [Referenced Param] -> Value # toEncodingList :: [Referenced Param] -> Encoding #
ToJSON (Referenced Schema)
Instance details Defined in Data.Swagger.Internal Methods toJSON :: Referenced Schema -> Value # toEncoding :: Referenced Schema -> Encoding # toJSONList :: [Referenced Schema] -> Value # toEncodingList :: [Referenced Schema] -> Encoding #
ToJSON (Referenced Response)
Instance details Defined in Data.Swagger.Internal Methods toJSON :: Referenced Response -> Value # toEncoding :: Referenced Response -> Encoding # toJSONList :: [Referenced Response] -> Value # toEncodingList :: [Referenced Response] -> Encoding #
(ToJSON a, ToJSON b) => ToJSON (Either a b)
Instance details Defined in Data.Aeson.Types.ToJSON Methods toJSON :: Either a b -> Value # toEncoding :: Either a b -> Encoding # toJSONList :: [Either a b] -> Value # toEncodingList :: [Either a b] -> Encoding #
(ToJSON a, ToJSON b) => ToJSON (a, b)
Instance details Defined in Data.Aeson.Types.ToJSON Methods toJSON :: (a, b) -> Value # toEncoding :: (a, b) -> Encoding # toJSONList :: [(a, b)] -> Value # toEncodingList :: [(a, b)] -> Encoding #
(ToJSON v, ToJSONKey k) => ToJSON (HashMap k v)
Instance details Defined in Data.Aeson.Types.ToJSON Methods toJSON :: HashMap k v -> Value # toEncoding :: HashMap k v -> Encoding # toJSONList :: [HashMap k v] -> Value # toEncodingList :: [HashMap k v] -> Encoding #
(ToJSON v, ToJSONKey k) => ToJSON (Map k v)
Instance details Defined in Data.Aeson.Types.ToJSON Methods toJSON :: Map k v -> Value # toEncoding :: Map k v -> Encoding # toJSONList :: [Map k v] -> Value # toEncodingList :: [Map k v] -> Encoding #
HasResolution a => ToJSON (Fixed a)
Instance details Defined in Data.Aeson.Types.ToJSON Methods toJSON :: Fixed a -> Value # toEncoding :: Fixed a -> Encoding # toJSONList :: [Fixed a] -> Value # toEncodingList :: [Fixed a] -> Encoding #
ToJSON (Proxy a)
Instance details Defined in Data.Aeson.Types.ToJSON Methods toJSON :: Proxy a -> Value # toEncoding :: Proxy a -> Encoding # toJSONList :: [Proxy a] -> Value # toEncodingList :: [Proxy a] -> Encoding #
(ToJSONKey k, ToJSON v) => ToJSON (InsOrdHashMap k v)
Instance details Defined in Data.HashMap.Strict.InsOrd Methods toJSON :: InsOrdHashMap k v -> Value # toEncoding :: InsOrdHashMap k v -> Encoding # toJSONList :: [InsOrdHashMap k v] -> Value # toEncodingList :: [InsOrdHashMap k v] -> Encoding #
(ToJSON a, ToJSON b) => ToJSON (Pair a b)	Since: aeson-1.5.3.0
Instance details Defined in Data.Aeson.Types.ToJSON Methods toJSON :: Pair a b -> Value # toEncoding :: Pair a b -> Encoding # toJSONList :: [Pair a b] -> Value # toEncodingList :: [Pair a b] -> Encoding #
(ToJSON a, ToJSON b) => ToJSON (These a b)	Since: aeson-1.5.3.0
Instance details Defined in Data.Aeson.Types.ToJSON Methods toJSON :: These a b -> Value # toEncoding :: These a b -> Encoding # toJSONList :: [These a b] -> Value # toEncodingList :: [These a b] -> Encoding #
(ToJSON a, ToJSON b) => ToJSON (Either a b)	Since: aeson-1.5.3.0
Instance details Defined in Data.Aeson.Types.ToJSON Methods toJSON :: Either a b -> Value # toEncoding :: Either a b -> Encoding # toJSONList :: [Either a b] -> Value # toEncodingList :: [Either a b] -> Encoding #
(ToJSON a, ToJSON b) => ToJSON (These a b)	Since: aeson-1.5.1.0
Instance details Defined in Data.Aeson.Types.ToJSON Methods toJSON :: These a b -> Value # toEncoding :: These a b -> Encoding # toJSONList :: [These a b] -> Value # toEncodingList :: [These a b] -> Encoding #
(ToJSON a, ToJSON b, ToJSON c) => ToJSON (a, b, c)
Instance details Defined in Data.Aeson.Types.ToJSON Methods toJSON :: (a, b, c) -> Value # toEncoding :: (a, b, c) -> Encoding # toJSONList :: [(a, b, c)] -> Value # toEncodingList :: [(a, b, c)] -> Encoding #
ToJSON a => ToJSON (Const a b)
Instance details Defined in Data.Aeson.Types.ToJSON Methods toJSON :: Const a b -> Value # toEncoding :: Const a b -> Encoding # toJSONList :: [Const a b] -> Value # toEncodingList :: [Const a b] -> Encoding #
ToJSON b => ToJSON (Tagged a b)
Instance details Defined in Data.Aeson.Types.ToJSON Methods toJSON :: Tagged a b -> Value # toEncoding :: Tagged a b -> Encoding # toJSONList :: [Tagged a b] -> Value # toEncodingList :: [Tagged a b] -> Encoding #
(ToJSON1 f, ToJSON1 g, ToJSON a) => ToJSON (These1 f g a)	Since: aeson-1.5.1.0
Instance details Defined in Data.Aeson.Types.ToJSON Methods toJSON :: These1 f g a -> Value # toEncoding :: These1 f g a -> Encoding # toJSONList :: [These1 f g a] -> Value # toEncodingList :: [These1 f g a] -> Encoding #
(ToJSON a, ToJSON b, ToJSON c, ToJSON d) => ToJSON (a, b, c, d)
Instance details Defined in Data.Aeson.Types.ToJSON Methods toJSON :: (a, b, c, d) -> Value # toEncoding :: (a, b, c, d) -> Encoding # toJSONList :: [(a, b, c, d)] -> Value # toEncodingList :: [(a, b, c, d)] -> Encoding #
(ToJSON1 f, ToJSON1 g, ToJSON a) => ToJSON (Product f g a)
Instance details Defined in Data.Aeson.Types.ToJSON Methods toJSON :: Product f g a -> Value # toEncoding :: Product f g a -> Encoding # toJSONList :: [Product f g a] -> Value # toEncodingList :: [Product f g a] -> Encoding #
(ToJSON1 f, ToJSON1 g, ToJSON a) => ToJSON (Sum f g a)
Instance details Defined in Data.Aeson.Types.ToJSON Methods toJSON :: Sum f g a -> Value # toEncoding :: Sum f g a -> Encoding # toJSONList :: [Sum f g a] -> Value # toEncodingList :: [Sum f g a] -> Encoding #
(ToJSON a, ToJSON b, ToJSON c, ToJSON d, ToJSON e) => ToJSON (a, b, c, d, e)
Instance details Defined in Data.Aeson.Types.ToJSON Methods toJSON :: (a, b, c, d, e) -> Value # toEncoding :: (a, b, c, d, e) -> Encoding # toJSONList :: [(a, b, c, d, e)] -> Value # toEncodingList :: [(a, b, c, d, e)] -> Encoding #
(ToJSON1 f, ToJSON1 g, ToJSON a) => ToJSON (Compose f g a)
Instance details Defined in Data.Aeson.Types.ToJSON Methods toJSON :: Compose f g a -> Value # toEncoding :: Compose f g a -> Encoding # toJSONList :: [Compose f g a] -> Value # toEncodingList :: [Compose f g a] -> Encoding #
(ToJSON a, ToJSON b, ToJSON c, ToJSON d, ToJSON e, ToJSON f) => ToJSON (a, b, c, d, e, f)
Instance details Defined in Data.Aeson.Types.ToJSON Methods toJSON :: (a, b, c, d, e, f) -> Value # toEncoding :: (a, b, c, d, e, f) -> Encoding # toJSONList :: [(a, b, c, d, e, f)] -> Value # toEncodingList :: [(a, b, c, d, e, f)] -> Encoding #
(ToJSON a, ToJSON b, ToJSON c, ToJSON d, ToJSON e, ToJSON f, ToJSON g) => ToJSON (a, b, c, d, e, f, g)
Instance details Defined in Data.Aeson.Types.ToJSON Methods toJSON :: (a, b, c, d, e, f, g) -> Value # toEncoding :: (a, b, c, d, e, f, g) -> Encoding # toJSONList :: [(a, b, c, d, e, f, g)] -> Value # toEncodingList :: [(a, b, c, d, e, f, g)] -> Encoding #
(ToJSON a, ToJSON b, ToJSON c, ToJSON d, ToJSON e, ToJSON f, ToJSON g, ToJSON h) => ToJSON (a, b, c, d, e, f, g, h)
Instance details Defined in Data.Aeson.Types.ToJSON Methods toJSON :: (a, b, c, d, e, f, g, h) -> Value # toEncoding :: (a, b, c, d, e, f, g, h) -> Encoding # toJSONList :: [(a, b, c, d, e, f, g, h)] -> Value # toEncodingList :: [(a, b, c, d, e, f, g, h)] -> Encoding #
(ToJSON a, ToJSON b, ToJSON c, ToJSON d, ToJSON e, ToJSON f, ToJSON g, ToJSON h, ToJSON i) => ToJSON (a, b, c, d, e, f, g, h, i)
Instance details Defined in Data.Aeson.Types.ToJSON Methods toJSON :: (a, b, c, d, e, f, g, h, i) -> Value # toEncoding :: (a, b, c, d, e, f, g, h, i) -> Encoding # toJSONList :: [(a, b, c, d, e, f, g, h, i)] -> Value # toEncodingList :: [(a, b, c, d, e, f, g, h, i)] -> Encoding #
(ToJSON a, ToJSON b, ToJSON c, ToJSON d, ToJSON e, ToJSON f, ToJSON g, ToJSON h, ToJSON i, ToJSON j) => ToJSON (a, b, c, d, e, f, g, h, i, j)
Instance details Defined in Data.Aeson.Types.ToJSON Methods toJSON :: (a, b, c, d, e, f, g, h, i, j) -> Value # toEncoding :: (a, b, c, d, e, f, g, h, i, j) -> Encoding # toJSONList :: [(a, b, c, d, e, f, g, h, i, j)] -> Value # toEncodingList :: [(a, b, c, d, e, f, g, h, i, j)] -> Encoding #
(ToJSON a, ToJSON b, ToJSON c, ToJSON d, ToJSON e, ToJSON f, ToJSON g, ToJSON h, ToJSON i, ToJSON j, ToJSON k) => ToJSON (a, b, c, d, e, f, g, h, i, j, k)
Instance details Defined in Data.Aeson.Types.ToJSON Methods toJSON :: (a, b, c, d, e, f, g, h, i, j, k) -> Value # toEncoding :: (a, b, c, d, e, f, g, h, i, j, k) -> Encoding # toJSONList :: [(a, b, c, d, e, f, g, h, i, j, k)] -> Value # toEncodingList :: [(a, b, c, d, e, f, g, h, i, j, k)] -> Encoding #
(ToJSON a, ToJSON b, ToJSON c, ToJSON d, ToJSON e, ToJSON f, ToJSON g, ToJSON h, ToJSON i, ToJSON j, ToJSON k, ToJSON l) => ToJSON (a, b, c, d, e, f, g, h, i, j, k, l)
Instance details Defined in Data.Aeson.Types.ToJSON Methods toJSON :: (a, b, c, d, e, f, g, h, i, j, k, l) -> Value # toEncoding :: (a, b, c, d, e, f, g, h, i, j, k, l) -> Encoding # toJSONList :: [(a, b, c, d, e, f, g, h, i, j, k, l)] -> Value # toEncodingList :: [(a, b, c, d, e, f, g, h, i, j, k, l)] -> Encoding #
(ToJSON a, ToJSON b, ToJSON c, ToJSON d, ToJSON e, ToJSON f, ToJSON g, ToJSON h, ToJSON i, ToJSON j, ToJSON k, ToJSON l, ToJSON m) => ToJSON (a, b, c, d, e, f, g, h, i, j, k, l, m)
Instance details Defined in Data.Aeson.Types.ToJSON Methods toJSON :: (a, b, c, d, e, f, g, h, i, j, k, l, m) -> Value # toEncoding :: (a, b, c, d, e, f, g, h, i, j, k, l, m) -> Encoding # toJSONList :: [(a, b, c, d, e, f, g, h, i, j, k, l, m)] -> Value # toEncodingList :: [(a, b, c, d, e, f, g, h, i, j, k, l, m)] -> Encoding #
(ToJSON a, ToJSON b, ToJSON c, ToJSON d, ToJSON e, ToJSON f, ToJSON g, ToJSON h, ToJSON i, ToJSON j, ToJSON k, ToJSON l, ToJSON m, ToJSON n) => ToJSON (a, b, c, d, e, f, g, h, i, j, k, l, m, n)
Instance details Defined in Data.Aeson.Types.ToJSON Methods toJSON :: (a, b, c, d, e, f, g, h, i, j, k, l, m, n) -> Value # toEncoding :: (a, b, c, d, e, f, g, h, i, j, k, l, m, n) -> Encoding # toJSONList :: [(a, b, c, d, e, f, g, h, i, j, k, l, m, n)] -> Value # toEncodingList :: [(a, b, c, d, e, f, g, h, i, j, k, l, m, n)] -> Encoding #
(ToJSON a, ToJSON b, ToJSON c, ToJSON d, ToJSON e, ToJSON f, ToJSON g, ToJSON h, ToJSON i, ToJSON j, ToJSON k, ToJSON l, ToJSON m, ToJSON n, ToJSON o) => ToJSON (a, b, c, d, e, f, g, h, i, j, k, l, m, n, o)
Instance details Defined in Data.Aeson.Types.ToJSON Methods toJSON :: (a, b, c, d, e, f, g, h, i, j, k, l, m, n, o) -> Value # toEncoding :: (a, b, c, d, e, f, g, h, i, j, k, l, m, n, o) -> Encoding # toJSONList :: [(a, b, c, d, e, f, g, h, i, j, k, l, m, n, o)] -> Value # toEncodingList :: [(a, b, c, d, e, f, g, h, i, j, k, l, m, n, o)] -> Encoding #

withText :: String -> (Text -> Parser a) -> Value -> Parser a #

withText name f value applies f to the Text when value is a String and fails otherwise.

Error message example

withText "MyType" f Null
-- Error: "parsing MyType failed, expected String, but encountered Null"

withObject :: String -> (Object -> Parser a) -> Value -> Parser a #

withObject name f value applies f to the Object when value is an Object and fails otherwise.

Error message example

withObject "MyType" f (String "oops")
-- Error: "parsing MyType failed, expected Object, but encountered String"

class FromJSON a #

A type that can be converted from JSON, with the possibility of failure.

In many cases, you can get the compiler to generate parsing code for you (see below). To begin, let's cover writing an instance by hand.

There are various reasons a conversion could fail. For example, an Object could be missing a required key, an Array could be of the wrong size, or a value could be of an incompatible type.

The basic ways to signal a failed conversion are as follows:

fail yields a custom error message: it is the recommended way of reporting a failure;
empty (or mzero) is uninformative: use it when the error is meant to be caught by some (<|>);
typeMismatch can be used to report a failure when the encountered value is not of the expected JSON type; unexpected is an appropriate alternative when more than one type may be expected, or to keep the expected type implicit.

prependFailure (or modifyFailure) add more information to a parser's error messages.

An example type and instance using typeMismatch and prependFailure:

-- Allow ourselves to write Text literals.
{-# LANGUAGE OverloadedStrings #-}

data Coord = Coord { x :: Double, y :: Double }

instance FromJSON Coord where
    parseJSON (Object v) = Coord
        <$> v .: "x"
        <*> v .: "y"

    -- We do not expect a non-Object value here.
    -- We could use empty to fail, but typeMismatch
    -- gives a much more informative error message.
    parseJSON invalid    =
        prependFailure "parsing Coord failed, "
            (typeMismatch "Object" invalid)

For this common case of only being concerned with a single type of JSON value, the functions withObject, withScientific, etc. are provided. Their use is to be preferred when possible, since they are more terse. Using withObject, we can rewrite the above instance (assuming the same language extension and data type) as:

instance FromJSON Coord where
    parseJSON = withObject "Coord" $ \v -> Coord
        <$> v .: "x"
        <*> v .: "y"

Instead of manually writing your FromJSON instance, there are two options to do it automatically:

Data.Aeson.TH provides Template Haskell functions which will derive an instance at compile time. The generated instance is optimized for your type so it will probably be more efficient than the following option.
The compiler can provide a default generic implementation for parseJSON.

To use the second, simply add a deriving Generic clause to your datatype and declare a FromJSON instance for your datatype without giving a definition for parseJSON.

For example, the previous example can be simplified to just:

{-# LANGUAGE DeriveGeneric #-}

import GHC.Generics

data Coord = Coord { x :: Double, y :: Double } deriving Generic

instance FromJSON Coord

The default implementation will be equivalent to parseJSON = genericParseJSON defaultOptions; if you need different options, you can customize the generic decoding by defining:

customOptions = defaultOptions
                { fieldLabelModifier = map toUpper
                }

instance FromJSON Coord where
    parseJSON = genericParseJSON customOptions

Instances

Instances details

FromJSON Bool
Instance details Defined in Data.Aeson.Types.FromJSON Methods parseJSON :: Value -> Parser Bool # parseJSONList :: Value -> Parser [Bool] #
FromJSON Char
Instance details Defined in Data.Aeson.Types.FromJSON Methods parseJSON :: Value -> Parser Char # parseJSONList :: Value -> Parser [Char] #
FromJSON Double
Instance details Defined in Data.Aeson.Types.FromJSON Methods parseJSON :: Value -> Parser Double # parseJSONList :: Value -> Parser [Double] #
FromJSON Float
Instance details Defined in Data.Aeson.Types.FromJSON Methods parseJSON :: Value -> Parser Float # parseJSONList :: Value -> Parser [Float] #
FromJSON Int
Instance details Defined in Data.Aeson.Types.FromJSON Methods parseJSON :: Value -> Parser Int # parseJSONList :: Value -> Parser [Int] #
FromJSON Int8
Instance details Defined in Data.Aeson.Types.FromJSON Methods parseJSON :: Value -> Parser Int8 # parseJSONList :: Value -> Parser [Int8] #
FromJSON Int16
Instance details Defined in Data.Aeson.Types.FromJSON Methods parseJSON :: Value -> Parser Int16 # parseJSONList :: Value -> Parser [Int16] #
FromJSON Int32
Instance details Defined in Data.Aeson.Types.FromJSON Methods parseJSON :: Value -> Parser Int32 # parseJSONList :: Value -> Parser [Int32] #
FromJSON Int64
Instance details Defined in Data.Aeson.Types.FromJSON Methods parseJSON :: Value -> Parser Int64 # parseJSONList :: Value -> Parser [Int64] #
FromJSON Integer	This instance includes a bounds check to prevent maliciously large inputs to fill up the memory of the target system. You can newtype `Scientific` and provide your own instance using `withScientific` if you want to allow larger inputs.
Instance details Defined in Data.Aeson.Types.FromJSON Methods parseJSON :: Value -> Parser Integer # parseJSONList :: Value -> Parser [Integer] #
FromJSON Natural
Instance details Defined in Data.Aeson.Types.FromJSON Methods parseJSON :: Value -> Parser Natural # parseJSONList :: Value -> Parser [Natural] #
FromJSON Ordering
Instance details Defined in Data.Aeson.Types.FromJSON Methods parseJSON :: Value -> Parser Ordering # parseJSONList :: Value -> Parser [Ordering] #
FromJSON Word
Instance details Defined in Data.Aeson.Types.FromJSON Methods parseJSON :: Value -> Parser Word # parseJSONList :: Value -> Parser [Word] #
FromJSON Word8
Instance details Defined in Data.Aeson.Types.FromJSON Methods parseJSON :: Value -> Parser Word8 # parseJSONList :: Value -> Parser [Word8] #
FromJSON Word16
Instance details Defined in Data.Aeson.Types.FromJSON Methods parseJSON :: Value -> Parser Word16 # parseJSONList :: Value -> Parser [Word16] #
FromJSON Word32
Instance details Defined in Data.Aeson.Types.FromJSON Methods parseJSON :: Value -> Parser Word32 # parseJSONList :: Value -> Parser [Word32] #
FromJSON Word64
Instance details Defined in Data.Aeson.Types.FromJSON Methods parseJSON :: Value -> Parser Word64 # parseJSONList :: Value -> Parser [Word64] #
FromJSON ()
Instance details Defined in Data.Aeson.Types.FromJSON Methods parseJSON :: Value -> Parser () # parseJSONList :: Value -> Parser [()] #
FromJSON Version
Instance details Defined in Data.Aeson.Types.FromJSON Methods parseJSON :: Value -> Parser Version # parseJSONList :: Value -> Parser [Version] #
FromJSON Scientific
Instance details Defined in Data.Aeson.Types.FromJSON Methods parseJSON :: Value -> Parser Scientific # parseJSONList :: Value -> Parser [Scientific] #
FromJSON Text
Instance details Defined in Data.Aeson.Types.FromJSON Methods parseJSON :: Value -> Parser Text # parseJSONList :: Value -> Parser [Text] #
FromJSON UTCTime
Instance details Defined in Data.Aeson.Types.FromJSON Methods parseJSON :: Value -> Parser UTCTime # parseJSONList :: Value -> Parser [UTCTime] #
FromJSON Value
Instance details Defined in Data.Aeson.Types.FromJSON Methods parseJSON :: Value -> Parser Value # parseJSONList :: Value -> Parser [Value] #
FromJSON DotNetTime
Instance details Defined in Data.Aeson.Types.FromJSON Methods parseJSON :: Value -> Parser DotNetTime # parseJSONList :: Value -> Parser [DotNetTime] #
FromJSON Text
Instance details Defined in Data.Aeson.Types.FromJSON Methods parseJSON :: Value -> Parser Text # parseJSONList :: Value -> Parser [Text] #
FromJSON Void
Instance details Defined in Data.Aeson.Types.FromJSON Methods parseJSON :: Value -> Parser Void # parseJSONList :: Value -> Parser [Void] #
FromJSON CTime
Instance details Defined in Data.Aeson.Types.FromJSON Methods parseJSON :: Value -> Parser CTime # parseJSONList :: Value -> Parser [CTime] #
FromJSON IntSet
Instance details Defined in Data.Aeson.Types.FromJSON Methods parseJSON :: Value -> Parser IntSet # parseJSONList :: Value -> Parser [IntSet] #
FromJSON PersistValue
Instance details Defined in Database.Persist.Types.Base Methods parseJSON :: Value -> Parser PersistValue # parseJSONList :: Value -> Parser [PersistValue] #
FromJSON MongoConf
Instance details Defined in Database.Persist.MongoDB Methods parseJSON :: Value -> Parser MongoConf # parseJSONList :: Value -> Parser [MongoConf] #
FromJSON Swagger
Instance details Defined in Data.Swagger.Internal Methods parseJSON :: Value -> Parser Swagger # parseJSONList :: Value -> Parser [Swagger] #
FromJSON Info
Instance details Defined in Data.Swagger.Internal Methods parseJSON :: Value -> Parser Info # parseJSONList :: Value -> Parser [Info] #
FromJSON Contact
Instance details Defined in Data.Swagger.Internal Methods parseJSON :: Value -> Parser Contact # parseJSONList :: Value -> Parser [Contact] #
FromJSON License
Instance details Defined in Data.Swagger.Internal Methods parseJSON :: Value -> Parser License # parseJSONList :: Value -> Parser [License] #
FromJSON Host
Instance details Defined in Data.Swagger.Internal Methods parseJSON :: Value -> Parser Host # parseJSONList :: Value -> Parser [Host] #
FromJSON Scheme
Instance details Defined in Data.Swagger.Internal Methods parseJSON :: Value -> Parser Scheme # parseJSONList :: Value -> Parser [Scheme] #
FromJSON PathItem
Instance details Defined in Data.Swagger.Internal Methods parseJSON :: Value -> Parser PathItem # parseJSONList :: Value -> Parser [PathItem] #
FromJSON Operation
Instance details Defined in Data.Swagger.Internal Methods parseJSON :: Value -> Parser Operation # parseJSONList :: Value -> Parser [Operation] #
FromJSON MimeList
Instance details Defined in Data.Swagger.Internal Methods parseJSON :: Value -> Parser MimeList # parseJSONList :: Value -> Parser [MimeList] #
FromJSON Param
Instance details Defined in Data.Swagger.Internal Methods parseJSON :: Value -> Parser Param # parseJSONList :: Value -> Parser [Param] #
FromJSON ParamAnySchema
Instance details Defined in Data.Swagger.Internal Methods parseJSON :: Value -> Parser ParamAnySchema # parseJSONList :: Value -> Parser [ParamAnySchema] #
FromJSON ParamOtherSchema
Instance details Defined in Data.Swagger.Internal Methods parseJSON :: Value -> Parser ParamOtherSchema # parseJSONList :: Value -> Parser [ParamOtherSchema] #
FromJSON ParamLocation
Instance details Defined in Data.Swagger.Internal Methods parseJSON :: Value -> Parser ParamLocation # parseJSONList :: Value -> Parser [ParamLocation] #
FromJSON Schema
Instance details Defined in Data.Swagger.Internal Methods parseJSON :: Value -> Parser Schema # parseJSONList :: Value -> Parser [Schema] #
FromJSON Xml
Instance details Defined in Data.Swagger.Internal Methods parseJSON :: Value -> Parser Xml # parseJSONList :: Value -> Parser [Xml] #
FromJSON Responses
Instance details Defined in Data.Swagger.Internal Methods parseJSON :: Value -> Parser Responses # parseJSONList :: Value -> Parser [Responses] #
FromJSON Response
Instance details Defined in Data.Swagger.Internal Methods parseJSON :: Value -> Parser Response # parseJSONList :: Value -> Parser [Response] #
FromJSON Header
Instance details Defined in Data.Swagger.Internal Methods parseJSON :: Value -> Parser Header # parseJSONList :: Value -> Parser [Header] #
FromJSON Example
Instance details Defined in Data.Swagger.Internal Methods parseJSON :: Value -> Parser Example # parseJSONList :: Value -> Parser [Example] #
FromJSON ApiKeyLocation
Instance details Defined in Data.Swagger.Internal Methods parseJSON :: Value -> Parser ApiKeyLocation # parseJSONList :: Value -> Parser [ApiKeyLocation] #
FromJSON ApiKeyParams
Instance details Defined in Data.Swagger.Internal Methods parseJSON :: Value -> Parser ApiKeyParams # parseJSONList :: Value -> Parser [ApiKeyParams] #
FromJSON OAuth2Flow
Instance details Defined in Data.Swagger.Internal Methods parseJSON :: Value -> Parser OAuth2Flow # parseJSONList :: Value -> Parser [OAuth2Flow] #
FromJSON OAuth2Params
Instance details Defined in Data.Swagger.Internal Methods parseJSON :: Value -> Parser OAuth2Params # parseJSONList :: Value -> Parser [OAuth2Params] #
FromJSON SecuritySchemeType
Instance details Defined in Data.Swagger.Internal Methods parseJSON :: Value -> Parser SecuritySchemeType # parseJSONList :: Value -> Parser [SecuritySchemeType] #
FromJSON SecurityScheme
Instance details Defined in Data.Swagger.Internal Methods parseJSON :: Value -> Parser SecurityScheme # parseJSONList :: Value -> Parser [SecurityScheme] #
FromJSON SecurityDefinitions
Instance details Defined in Data.Swagger.Internal Methods parseJSON :: Value -> Parser SecurityDefinitions # parseJSONList :: Value -> Parser [SecurityDefinitions] #
FromJSON SecurityRequirement
Instance details Defined in Data.Swagger.Internal Methods parseJSON :: Value -> Parser SecurityRequirement # parseJSONList :: Value -> Parser [SecurityRequirement] #
FromJSON Tag
Instance details Defined in Data.Swagger.Internal Methods parseJSON :: Value -> Parser Tag # parseJSONList :: Value -> Parser [Tag] #
FromJSON ExternalDocs
Instance details Defined in Data.Swagger.Internal Methods parseJSON :: Value -> Parser ExternalDocs # parseJSONList :: Value -> Parser [ExternalDocs] #
FromJSON Reference
Instance details Defined in Data.Swagger.Internal Methods parseJSON :: Value -> Parser Reference # parseJSONList :: Value -> Parser [Reference] #
FromJSON URL
Instance details Defined in Data.Swagger.Internal Methods parseJSON :: Value -> Parser URL # parseJSONList :: Value -> Parser [URL] #
FromJSON AdditionalProperties
Instance details Defined in Data.Swagger.Internal Methods parseJSON :: Value -> Parser AdditionalProperties # parseJSONList :: Value -> Parser [AdditionalProperties] #
FromJSON ZonedTime	Supported string formats: `YYYY-MM-DD HH:MM Z` `YYYY-MM-DD HH:MM:SS Z` `YYYY-MM-DD HH:MM:SS.SSS Z` The first space may instead be a `T`, and the second space is optional. The `Z` represents UTC. The `Z` may be replaced with a time zone offset of the form `+0000` or `-08:00`, where the first two digits are hours, the `:` is optional and the second two digits (also optional) are minutes.
Instance details Defined in Data.Aeson.Types.FromJSON Methods parseJSON :: Value -> Parser ZonedTime # parseJSONList :: Value -> Parser [ZonedTime] #
FromJSON LocalTime
Instance details Defined in Data.Aeson.Types.FromJSON Methods parseJSON :: Value -> Parser LocalTime # parseJSONList :: Value -> Parser [LocalTime] #
FromJSON TimeOfDay
Instance details Defined in Data.Aeson.Types.FromJSON Methods parseJSON :: Value -> Parser TimeOfDay # parseJSONList :: Value -> Parser [TimeOfDay] #
FromJSON CalendarDiffTime
Instance details Defined in Data.Aeson.Types.FromJSON Methods parseJSON :: Value -> Parser CalendarDiffTime # parseJSONList :: Value -> Parser [CalendarDiffTime] #
FromJSON SystemTime
Instance details Defined in Data.Aeson.Types.FromJSON Methods parseJSON :: Value -> Parser SystemTime # parseJSONList :: Value -> Parser [SystemTime] #
FromJSON NominalDiffTime	This instance includes a bounds check to prevent maliciously large inputs to fill up the memory of the target system. You can newtype `Scientific` and provide your own instance using `withScientific` if you want to allow larger inputs.
Instance details Defined in Data.Aeson.Types.FromJSON Methods parseJSON :: Value -> Parser NominalDiffTime # parseJSONList :: Value -> Parser [NominalDiffTime] #
FromJSON DiffTime	This instance includes a bounds check to prevent maliciously large inputs to fill up the memory of the target system. You can newtype `Scientific` and provide your own instance using `withScientific` if you want to allow larger inputs.
Instance details Defined in Data.Aeson.Types.FromJSON Methods parseJSON :: Value -> Parser DiffTime # parseJSONList :: Value -> Parser [DiffTime] #
FromJSON DayOfWeek
Instance details Defined in Data.Aeson.Types.FromJSON Methods parseJSON :: Value -> Parser DayOfWeek # parseJSONList :: Value -> Parser [DayOfWeek] #
FromJSON Day
Instance details Defined in Data.Aeson.Types.FromJSON Methods parseJSON :: Value -> Parser Day # parseJSONList :: Value -> Parser [Day] #
FromJSON CalendarDiffDays
Instance details Defined in Data.Aeson.Types.FromJSON Methods parseJSON :: Value -> Parser CalendarDiffDays # parseJSONList :: Value -> Parser [CalendarDiffDays] #
FromJSON UUID
Instance details Defined in Data.Aeson.Types.FromJSON Methods parseJSON :: Value -> Parser UUID # parseJSONList :: Value -> Parser [UUID] #
FromJSON NoOrphanNominalDiffTime
Instance details Defined in Database.Persist.MongoDB Methods parseJSON :: Value -> Parser NoOrphanNominalDiffTime # parseJSONList :: Value -> Parser [NoOrphanNominalDiffTime] #
FromJSON NoOrphanPortID
Instance details Defined in Database.Persist.MongoDB Methods parseJSON :: Value -> Parser NoOrphanPortID # parseJSONList :: Value -> Parser [NoOrphanPortID] #
FromJSON a => FromJSON [a]
Instance details Defined in Data.Aeson.Types.FromJSON Methods parseJSON :: Value -> Parser [a] # parseJSONList :: Value -> Parser [[a]] #
FromJSON a => FromJSON (Maybe a)
Instance details Defined in Data.Aeson.Types.FromJSON Methods parseJSON :: Value -> Parser (Maybe a) # parseJSONList :: Value -> Parser [Maybe a] #
(FromJSON a, Integral a) => FromJSON (Ratio a)
Instance details Defined in Data.Aeson.Types.FromJSON Methods parseJSON :: Value -> Parser (Ratio a) # parseJSONList :: Value -> Parser [Ratio a] #
FromJSON a => FromJSON (Min a)
Instance details Defined in Data.Aeson.Types.FromJSON Methods parseJSON :: Value -> Parser (Min a) # parseJSONList :: Value -> Parser [Min a] #
FromJSON a => FromJSON (Max a)
Instance details Defined in Data.Aeson.Types.FromJSON Methods parseJSON :: Value -> Parser (Max a) # parseJSONList :: Value -> Parser [Max a] #
FromJSON a => FromJSON (First a)
Instance details Defined in Data.Aeson.Types.FromJSON Methods parseJSON :: Value -> Parser (First a) # parseJSONList :: Value -> Parser [First a] #
FromJSON a => FromJSON (Last a)
Instance details Defined in Data.Aeson.Types.FromJSON Methods parseJSON :: Value -> Parser (Last a) # parseJSONList :: Value -> Parser [Last a] #
FromJSON a => FromJSON (WrappedMonoid a)
Instance details Defined in Data.Aeson.Types.FromJSON Methods parseJSON :: Value -> Parser (WrappedMonoid a) # parseJSONList :: Value -> Parser [WrappedMonoid a] #
FromJSON a => FromJSON (Option a)
Instance details Defined in Data.Aeson.Types.FromJSON Methods parseJSON :: Value -> Parser (Option a) # parseJSONList :: Value -> Parser [Option a] #
FromJSON a => FromJSON (Identity a)
Instance details Defined in Data.Aeson.Types.FromJSON Methods parseJSON :: Value -> Parser (Identity a) # parseJSONList :: Value -> Parser [Identity a] #
FromJSON a => FromJSON (First a)
Instance details Defined in Data.Aeson.Types.FromJSON Methods parseJSON :: Value -> Parser (First a) # parseJSONList :: Value -> Parser [First a] #
FromJSON a => FromJSON (Last a)
Instance details Defined in Data.Aeson.Types.FromJSON Methods parseJSON :: Value -> Parser (Last a) # parseJSONList :: Value -> Parser [Last a] #
FromJSON a => FromJSON (Dual a)
Instance details Defined in Data.Aeson.Types.FromJSON Methods parseJSON :: Value -> Parser (Dual a) # parseJSONList :: Value -> Parser [Dual a] #
FromJSON a => FromJSON (NonEmpty a)
Instance details Defined in Data.Aeson.Types.FromJSON Methods parseJSON :: Value -> Parser (NonEmpty a) # parseJSONList :: Value -> Parser [NonEmpty a] #
FromJSON a => FromJSON (IntMap a)
Instance details Defined in Data.Aeson.Types.FromJSON Methods parseJSON :: Value -> Parser (IntMap a) # parseJSONList :: Value -> Parser [IntMap a] #
FromJSON v => FromJSON (Tree v)
Instance details Defined in Data.Aeson.Types.FromJSON Methods parseJSON :: Value -> Parser (Tree v) # parseJSONList :: Value -> Parser [Tree v] #
FromJSON a => FromJSON (Seq a)
Instance details Defined in Data.Aeson.Types.FromJSON Methods parseJSON :: Value -> Parser (Seq a) # parseJSONList :: Value -> Parser [Seq a] #
(Ord a, FromJSON a) => FromJSON (Set a)
Instance details Defined in Data.Aeson.Types.FromJSON Methods parseJSON :: Value -> Parser (Set a) # parseJSONList :: Value -> Parser [Set a] #
FromJSON1 f => FromJSON (Fix f)	Since: aeson-1.5.3.0
Instance details Defined in Data.Aeson.Types.FromJSON Methods parseJSON :: Value -> Parser (Fix f) # parseJSONList :: Value -> Parser [Fix f] #
(FromJSON1 f, Functor f) => FromJSON (Mu f)	Since: aeson-1.5.3.0
Instance details Defined in Data.Aeson.Types.FromJSON Methods parseJSON :: Value -> Parser (Mu f) # parseJSONList :: Value -> Parser [Mu f] #
(FromJSON1 f, Functor f) => FromJSON (Nu f)	Since: aeson-1.5.3.0
Instance details Defined in Data.Aeson.Types.FromJSON Methods parseJSON :: Value -> Parser (Nu f) # parseJSONList :: Value -> Parser [Nu f] #
FromJSON a => FromJSON (DNonEmpty a)	Since: aeson-1.5.3.0
Instance details Defined in Data.Aeson.Types.FromJSON Methods parseJSON :: Value -> Parser (DNonEmpty a) # parseJSONList :: Value -> Parser [DNonEmpty a] #
FromJSON a => FromJSON (DList a)
Instance details Defined in Data.Aeson.Types.FromJSON Methods parseJSON :: Value -> Parser (DList a) # parseJSONList :: Value -> Parser [DList a] #
(Eq a, Hashable a, FromJSON a) => FromJSON (HashSet a)
Instance details Defined in Data.Aeson.Types.FromJSON Methods parseJSON :: Value -> Parser (HashSet a) # parseJSONList :: Value -> Parser [HashSet a] #
(Eq a, Hashable a, FromJSON a) => FromJSON (InsOrdHashSet a)
Instance details Defined in Data.HashSet.InsOrd Methods parseJSON :: Value -> Parser (InsOrdHashSet a) # parseJSONList :: Value -> Parser [InsOrdHashSet a] #
(Prim a, FromJSON a) => FromJSON (Vector a)
Instance details Defined in Data.Aeson.Types.FromJSON Methods parseJSON :: Value -> Parser (Vector a) # parseJSONList :: Value -> Parser [Vector a] #
(Storable a, FromJSON a) => FromJSON (Vector a)
Instance details Defined in Data.Aeson.Types.FromJSON Methods parseJSON :: Value -> Parser (Vector a) # parseJSONList :: Value -> Parser [Vector a] #
(Vector Vector a, FromJSON a) => FromJSON (Vector a)
Instance details Defined in Data.Aeson.Types.FromJSON Methods parseJSON :: Value -> Parser (Vector a) # parseJSONList :: Value -> Parser [Vector a] #
FromJSON a => FromJSON (Vector a)
Instance details Defined in Data.Aeson.Types.FromJSON Methods parseJSON :: Value -> Parser (Vector a) # parseJSONList :: Value -> Parser [Vector a] #
(Prim a, FromJSON a) => FromJSON (PrimArray a)
Instance details Defined in Data.Aeson.Types.FromJSON Methods parseJSON :: Value -> Parser (PrimArray a) # parseJSONList :: Value -> Parser [PrimArray a] #
FromJSON a => FromJSON (SmallArray a)
Instance details Defined in Data.Aeson.Types.FromJSON Methods parseJSON :: Value -> Parser (SmallArray a) # parseJSONList :: Value -> Parser [SmallArray a] #
FromJSON a => FromJSON (Array a)
Instance details Defined in Data.Aeson.Types.FromJSON Methods parseJSON :: Value -> Parser (Array a) # parseJSONList :: Value -> Parser [Array a] #
FromJSON a => FromJSON (Maybe a)	Since: aeson-1.5.3.0
Instance details Defined in Data.Aeson.Types.FromJSON Methods parseJSON :: Value -> Parser (Maybe a) # parseJSONList :: Value -> Parser [Maybe a] #
FromJSON (SwaggerItems ('SwaggerKindSchema :: SwaggerKind Type))	`>>>` `decode "{}" :: Maybe (SwaggerItems 'SwaggerKindSchema)`Just (SwaggerItemsArray []) `>>>` `eitherDecode "{\"$ref\":\"#/definitions/example\"}" :: Either String (SwaggerItems 'SwaggerKindSchema)`Right (SwaggerItemsObject (Ref (Reference {getReference = "example"}))) `>>>` `eitherDecode "[{\"$ref\":\"#/definitions/example\"}]" :: Either String (SwaggerItems 'SwaggerKindSchema)`Right (SwaggerItemsArray [Ref (Reference {getReference = "example"})])
Instance details Defined in Data.Swagger.Internal Methods parseJSON :: Value -> Parser (SwaggerItems 'SwaggerKindSchema) # parseJSONList :: Value -> Parser [SwaggerItems 'SwaggerKindSchema] #
FromJSON (SwaggerItems ('SwaggerKindParamOtherSchema :: SwaggerKind Type))
Instance details Defined in Data.Swagger.Internal Methods parseJSON :: Value -> Parser (SwaggerItems 'SwaggerKindParamOtherSchema) # parseJSONList :: Value -> Parser [SwaggerItems 'SwaggerKindParamOtherSchema] #
(FromJSON (CollectionFormat ('SwaggerKindNormal t)), FromJSON (ParamSchema ('SwaggerKindNormal t))) => FromJSON (SwaggerItems ('SwaggerKindNormal t))
Instance details Defined in Data.Swagger.Internal Methods parseJSON :: Value -> Parser (SwaggerItems ('SwaggerKindNormal t)) # parseJSONList :: Value -> Parser [SwaggerItems ('SwaggerKindNormal t)] #
FromJSON (SwaggerType ('SwaggerKindSchema :: SwaggerKind Type))
Instance details Defined in Data.Swagger.Internal Methods parseJSON :: Value -> Parser (SwaggerType 'SwaggerKindSchema) # parseJSONList :: Value -> Parser [SwaggerType 'SwaggerKindSchema] #
FromJSON (SwaggerType ('SwaggerKindParamOtherSchema :: SwaggerKind Type))
Instance details Defined in Data.Swagger.Internal Methods parseJSON :: Value -> Parser (SwaggerType 'SwaggerKindParamOtherSchema) # parseJSONList :: Value -> Parser [SwaggerType 'SwaggerKindParamOtherSchema] #
FromJSON (SwaggerType ('SwaggerKindNormal t))
Instance details Defined in Data.Swagger.Internal Methods parseJSON :: Value -> Parser (SwaggerType ('SwaggerKindNormal t)) # parseJSONList :: Value -> Parser [SwaggerType ('SwaggerKindNormal t)] #
FromJSON (CollectionFormat ('SwaggerKindParamOtherSchema :: SwaggerKind Type))
Instance details Defined in Data.Swagger.Internal Methods parseJSON :: Value -> Parser (CollectionFormat 'SwaggerKindParamOtherSchema) # parseJSONList :: Value -> Parser [CollectionFormat 'SwaggerKindParamOtherSchema] #
FromJSON (CollectionFormat ('SwaggerKindNormal t))
Instance details Defined in Data.Swagger.Internal Methods parseJSON :: Value -> Parser (CollectionFormat ('SwaggerKindNormal t)) # parseJSONList :: Value -> Parser [CollectionFormat ('SwaggerKindNormal t)] #
FromJSON (ParamSchema ('SwaggerKindSchema :: SwaggerKind Type))
Instance details Defined in Data.Swagger.Internal Methods parseJSON :: Value -> Parser (ParamSchema 'SwaggerKindSchema) # parseJSONList :: Value -> Parser [ParamSchema 'SwaggerKindSchema] #
FromJSON (ParamSchema ('SwaggerKindParamOtherSchema :: SwaggerKind Type))
Instance details Defined in Data.Swagger.Internal Methods parseJSON :: Value -> Parser (ParamSchema 'SwaggerKindParamOtherSchema) # parseJSONList :: Value -> Parser [ParamSchema 'SwaggerKindParamOtherSchema] #
(FromJSON (SwaggerType ('SwaggerKindNormal t)), FromJSON (SwaggerItems ('SwaggerKindNormal t))) => FromJSON (ParamSchema ('SwaggerKindNormal t))
Instance details Defined in Data.Swagger.Internal Methods parseJSON :: Value -> Parser (ParamSchema ('SwaggerKindNormal t)) # parseJSONList :: Value -> Parser [ParamSchema ('SwaggerKindNormal t)] #
FromJSON (Referenced Param)
Instance details Defined in Data.Swagger.Internal Methods parseJSON :: Value -> Parser (Referenced Param) # parseJSONList :: Value -> Parser [Referenced Param] #
FromJSON (Referenced Schema)
Instance details Defined in Data.Swagger.Internal Methods parseJSON :: Value -> Parser (Referenced Schema) # parseJSONList :: Value -> Parser [Referenced Schema] #
FromJSON (Referenced Response)
Instance details Defined in Data.Swagger.Internal Methods parseJSON :: Value -> Parser (Referenced Response) # parseJSONList :: Value -> Parser [Referenced Response] #
(FromJSON a, FromJSON b) => FromJSON (Either a b)
Instance details Defined in Data.Aeson.Types.FromJSON Methods parseJSON :: Value -> Parser (Either a b) # parseJSONList :: Value -> Parser [Either a b] #
(FromJSON a, FromJSON b) => FromJSON (a, b)
Instance details Defined in Data.Aeson.Types.FromJSON Methods parseJSON :: Value -> Parser (a, b) # parseJSONList :: Value -> Parser [(a, b)] #
(FromJSON v, FromJSONKey k, Eq k, Hashable k) => FromJSON (HashMap k v)
Instance details Defined in Data.Aeson.Types.FromJSON Methods parseJSON :: Value -> Parser (HashMap k v) # parseJSONList :: Value -> Parser [HashMap k v] #
(FromJSONKey k, Ord k, FromJSON v) => FromJSON (Map k v)
Instance details Defined in Data.Aeson.Types.FromJSON Methods parseJSON :: Value -> Parser (Map k v) # parseJSONList :: Value -> Parser [Map k v] #
HasResolution a => FromJSON (Fixed a)	This instance includes a bounds check to prevent maliciously large inputs to fill up the memory of the target system. You can newtype `Scientific` and provide your own instance using `withScientific` if you want to allow larger inputs.
Instance details Defined in Data.Aeson.Types.FromJSON Methods parseJSON :: Value -> Parser (Fixed a) # parseJSONList :: Value -> Parser [Fixed a] #
FromJSON (Proxy a)
Instance details Defined in Data.Aeson.Types.FromJSON Methods parseJSON :: Value -> Parser (Proxy a) # parseJSONList :: Value -> Parser [Proxy a] #
(Eq k, Hashable k, FromJSONKey k, FromJSON v) => FromJSON (InsOrdHashMap k v)
Instance details Defined in Data.HashMap.Strict.InsOrd Methods parseJSON :: Value -> Parser (InsOrdHashMap k v) # parseJSONList :: Value -> Parser [InsOrdHashMap k v] #
(FromJSON a, FromJSON b) => FromJSON (Pair a b)	Since: aeson-1.5.3.0
Instance details Defined in Data.Aeson.Types.FromJSON Methods parseJSON :: Value -> Parser (Pair a b) # parseJSONList :: Value -> Parser [Pair a b] #
(FromJSON a, FromJSON b) => FromJSON (These a b)	Since: aeson-1.5.3.0
Instance details Defined in Data.Aeson.Types.FromJSON Methods parseJSON :: Value -> Parser (These a b) # parseJSONList :: Value -> Parser [These a b] #
(FromJSON a, FromJSON b) => FromJSON (Either a b)	Since: aeson-1.5.3.0
Instance details Defined in Data.Aeson.Types.FromJSON Methods parseJSON :: Value -> Parser (Either a b) # parseJSONList :: Value -> Parser [Either a b] #
(FromJSON a, FromJSON b) => FromJSON (These a b)	Since: aeson-1.5.1.0
Instance details Defined in Data.Aeson.Types.FromJSON Methods parseJSON :: Value -> Parser (These a b) # parseJSONList :: Value -> Parser [These a b] #
(FromJSON a, FromJSON b, FromJSON c) => FromJSON (a, b, c)
Instance details Defined in Data.Aeson.Types.FromJSON Methods parseJSON :: Value -> Parser (a, b, c) # parseJSONList :: Value -> Parser [(a, b, c)] #
FromJSON a => FromJSON (Const a b)
Instance details Defined in Data.Aeson.Types.FromJSON Methods parseJSON :: Value -> Parser (Const a b) # parseJSONList :: Value -> Parser [Const a b] #
FromJSON b => FromJSON (Tagged a b)
Instance details Defined in Data.Aeson.Types.FromJSON Methods parseJSON :: Value -> Parser (Tagged a b) # parseJSONList :: Value -> Parser [Tagged a b] #
(FromJSON1 f, FromJSON1 g, FromJSON a) => FromJSON (These1 f g a)	Since: aeson-1.5.1.0
Instance details Defined in Data.Aeson.Types.FromJSON Methods parseJSON :: Value -> Parser (These1 f g a) # parseJSONList :: Value -> Parser [These1 f g a] #
(FromJSON a, FromJSON b, FromJSON c, FromJSON d) => FromJSON (a, b, c, d)
Instance details Defined in Data.Aeson.Types.FromJSON Methods parseJSON :: Value -> Parser (a, b, c, d) # parseJSONList :: Value -> Parser [(a, b, c, d)] #
(FromJSON1 f, FromJSON1 g, FromJSON a) => FromJSON (Product f g a)
Instance details Defined in Data.Aeson.Types.FromJSON Methods parseJSON :: Value -> Parser (Product f g a) # parseJSONList :: Value -> Parser [Product f g a] #
(FromJSON1 f, FromJSON1 g, FromJSON a) => FromJSON (Sum f g a)
Instance details Defined in Data.Aeson.Types.FromJSON Methods parseJSON :: Value -> Parser (Sum f g a) # parseJSONList :: Value -> Parser [Sum f g a] #
(FromJSON a, FromJSON b, FromJSON c, FromJSON d, FromJSON e) => FromJSON (a, b, c, d, e)
Instance details Defined in Data.Aeson.Types.FromJSON Methods parseJSON :: Value -> Parser (a, b, c, d, e) # parseJSONList :: Value -> Parser [(a, b, c, d, e)] #
(FromJSON1 f, FromJSON1 g, FromJSON a) => FromJSON (Compose f g a)
Instance details Defined in Data.Aeson.Types.FromJSON Methods parseJSON :: Value -> Parser (Compose f g a) # parseJSONList :: Value -> Parser [Compose f g a] #
(FromJSON a, FromJSON b, FromJSON c, FromJSON d, FromJSON e, FromJSON f) => FromJSON (a, b, c, d, e, f)
Instance details Defined in Data.Aeson.Types.FromJSON Methods parseJSON :: Value -> Parser (a, b, c, d, e, f) # parseJSONList :: Value -> Parser [(a, b, c, d, e, f)] #
(FromJSON a, FromJSON b, FromJSON c, FromJSON d, FromJSON e, FromJSON f, FromJSON g) => FromJSON (a, b, c, d, e, f, g)
Instance details Defined in Data.Aeson.Types.FromJSON Methods parseJSON :: Value -> Parser (a, b, c, d, e, f, g) # parseJSONList :: Value -> Parser [(a, b, c, d, e, f, g)] #
(FromJSON a, FromJSON b, FromJSON c, FromJSON d, FromJSON e, FromJSON f, FromJSON g, FromJSON h) => FromJSON (a, b, c, d, e, f, g, h)
Instance details Defined in Data.Aeson.Types.FromJSON Methods parseJSON :: Value -> Parser (a, b, c, d, e, f, g, h) # parseJSONList :: Value -> Parser [(a, b, c, d, e, f, g, h)] #
(FromJSON a, FromJSON b, FromJSON c, FromJSON d, FromJSON e, FromJSON f, FromJSON g, FromJSON h, FromJSON i) => FromJSON (a, b, c, d, e, f, g, h, i)
Instance details Defined in Data.Aeson.Types.FromJSON Methods parseJSON :: Value -> Parser (a, b, c, d, e, f, g, h, i) # parseJSONList :: Value -> Parser [(a, b, c, d, e, f, g, h, i)] #
(FromJSON a, FromJSON b, FromJSON c, FromJSON d, FromJSON e, FromJSON f, FromJSON g, FromJSON h, FromJSON i, FromJSON j) => FromJSON (a, b, c, d, e, f, g, h, i, j)
Instance details Defined in Data.Aeson.Types.FromJSON Methods parseJSON :: Value -> Parser (a, b, c, d, e, f, g, h, i, j) # parseJSONList :: Value -> Parser [(a, b, c, d, e, f, g, h, i, j)] #
(FromJSON a, FromJSON b, FromJSON c, FromJSON d, FromJSON e, FromJSON f, FromJSON g, FromJSON h, FromJSON i, FromJSON j, FromJSON k) => FromJSON (a, b, c, d, e, f, g, h, i, j, k)
Instance details Defined in Data.Aeson.Types.FromJSON Methods parseJSON :: Value -> Parser (a, b, c, d, e, f, g, h, i, j, k) # parseJSONList :: Value -> Parser [(a, b, c, d, e, f, g, h, i, j, k)] #
(FromJSON a, FromJSON b, FromJSON c, FromJSON d, FromJSON e, FromJSON f, FromJSON g, FromJSON h, FromJSON i, FromJSON j, FromJSON k, FromJSON l) => FromJSON (a, b, c, d, e, f, g, h, i, j, k, l)
Instance details Defined in Data.Aeson.Types.FromJSON Methods parseJSON :: Value -> Parser (a, b, c, d, e, f, g, h, i, j, k, l) # parseJSONList :: Value -> Parser [(a, b, c, d, e, f, g, h, i, j, k, l)] #
(FromJSON a, FromJSON b, FromJSON c, FromJSON d, FromJSON e, FromJSON f, FromJSON g, FromJSON h, FromJSON i, FromJSON j, FromJSON k, FromJSON l, FromJSON m) => FromJSON (a, b, c, d, e, f, g, h, i, j, k, l, m)
Instance details Defined in Data.Aeson.Types.FromJSON Methods parseJSON :: Value -> Parser (a, b, c, d, e, f, g, h, i, j, k, l, m) # parseJSONList :: Value -> Parser [(a, b, c, d, e, f, g, h, i, j, k, l, m)] #
(FromJSON a, FromJSON b, FromJSON c, FromJSON d, FromJSON e, FromJSON f, FromJSON g, FromJSON h, FromJSON i, FromJSON j, FromJSON k, FromJSON l, FromJSON m, FromJSON n) => FromJSON (a, b, c, d, e, f, g, h, i, j, k, l, m, n)
Instance details Defined in Data.Aeson.Types.FromJSON Methods parseJSON :: Value -> Parser (a, b, c, d, e, f, g, h, i, j, k, l, m, n) # parseJSONList :: Value -> Parser [(a, b, c, d, e, f, g, h, i, j, k, l, m, n)] #
(FromJSON a, FromJSON b, FromJSON c, FromJSON d, FromJSON e, FromJSON f, FromJSON g, FromJSON h, FromJSON i, FromJSON j, FromJSON k, FromJSON l, FromJSON m, FromJSON n, FromJSON o) => FromJSON (a, b, c, d, e, f, g, h, i, j, k, l, m, n, o)
Instance details Defined in Data.Aeson.Types.FromJSON Methods parseJSON :: Value -> Parser (a, b, c, d, e, f, g, h, i, j, k, l, m, n, o) # parseJSONList :: Value -> Parser [(a, b, c, d, e, f, g, h, i, j, k, l, m, n, o)] #

data Parser a #

A JSON parser. N.B. This might not fit your usual understanding of "parser". Instead you might like to think of Parser as a "parse result", i.e. a parser to which the input has already been applied.

Instances

Instances details

Monad Parser
Instance details Defined in Data.Aeson.Types.Internal Methods (>>=) :: Parser a -> (a -> Parser b) -> Parser b # (>>) :: Parser a -> Parser b -> Parser b # return :: a -> Parser a #
Functor Parser
Instance details Defined in Data.Aeson.Types.Internal Methods fmap :: (a -> b) -> Parser a -> Parser b # (<$) :: a -> Parser b -> Parser a #
MonadFail Parser
Instance details Defined in Data.Aeson.Types.Internal Methods fail :: String -> Parser a #
Applicative Parser
Instance details Defined in Data.Aeson.Types.Internal Methods pure :: a -> Parser a # (<>) :: Parser (a -> b) -> Parser a -> Parser b # liftA2 :: (a -> b -> c) -> Parser a -> Parser b -> Parser c # (>) :: Parser a -> Parser b -> Parser b # (<*) :: Parser a -> Parser b -> Parser a #
MonadPlus Parser
Instance details Defined in Data.Aeson.Types.Internal Methods mzero :: Parser a # mplus :: Parser a -> Parser a -> Parser a #
Alternative Parser
Instance details Defined in Data.Aeson.Types.Internal Methods empty :: Parser a # (<\|>) :: Parser a -> Parser a -> Parser a # some :: Parser a -> Parser [a] # many :: Parser a -> Parser [a] #
Semigroup (Parser a)
Instance details Defined in Data.Aeson.Types.Internal Methods (<>) :: Parser a -> Parser a -> Parser a # sconcat :: NonEmpty (Parser a) -> Parser a # stimes :: Integral b => b -> Parser a -> Parser a #
Monoid (Parser a)
Instance details Defined in Data.Aeson.Types.Internal Methods mempty :: Parser a # mappend :: Parser a -> Parser a -> Parser a # mconcat :: [Parser a] -> Parser a #

jsonEitherDecode :: FromJSON a => ByteString -> Either String a Source #

jsonEncode :: ToJSON a => a -> ByteString Source #