| Safe Haskell | None |
|---|---|
| Language | Haskell2010 |
Data.Aeson.Types.ToJSON
Synopsis
- class ToJSON a where
- toJSON :: a -> Value
- toEncoding :: a -> Encoding
- toJSONList :: [a] -> Value
- toEncodingList :: [a] -> Encoding
- class ToJSON1 f where
- liftToJSON :: (a -> Value) -> ([a] -> Value) -> f a -> Value
- liftToJSONList :: (a -> Value) -> ([a] -> Value) -> [f a] -> Value
- liftToEncoding :: (a -> Encoding) -> ([a] -> Encoding) -> f a -> Encoding
- liftToEncodingList :: (a -> Encoding) -> ([a] -> Encoding) -> [f a] -> Encoding
- toJSON1 :: (ToJSON1 f, ToJSON a) => f a -> Value
- toEncoding1 :: (ToJSON1 f, ToJSON a) => f a -> Encoding
- class ToJSON2 f where
- liftToJSON2 :: (a -> Value) -> ([a] -> Value) -> (b -> Value) -> ([b] -> Value) -> f a b -> Value
- liftToJSONList2 :: (a -> Value) -> ([a] -> Value) -> (b -> Value) -> ([b] -> Value) -> [f a b] -> Value
- liftToEncoding2 :: (a -> Encoding) -> ([a] -> Encoding) -> (b -> Encoding) -> ([b] -> Encoding) -> f a b -> Encoding
- liftToEncodingList2 :: (a -> Encoding) -> ([a] -> Encoding) -> (b -> Encoding) -> ([b] -> Encoding) -> [f a b] -> Encoding
- toJSON2 :: (ToJSON2 f, ToJSON a, ToJSON b) => f a b -> Value
- toEncoding2 :: (ToJSON2 f, ToJSON a, ToJSON b) => f a b -> Encoding
- class GToJSON' enc arity f where
- data ToArgs res arity a where
- genericToJSON :: (Generic a, GToJSON' Value Zero (Rep a)) => Options -> a -> Value
- genericToEncoding :: (Generic a, GToJSON' Encoding Zero (Rep a)) => Options -> a -> Encoding
- genericLiftToJSON :: (Generic1 f, GToJSON' Value One (Rep1 f)) => Options -> (a -> Value) -> ([a] -> Value) -> f a -> Value
- genericLiftToEncoding :: (Generic1 f, GToJSON' Encoding One (Rep1 f)) => Options -> (a -> Encoding) -> ([a] -> Encoding) -> f a -> Encoding
- class ToJSONKey a where
- toJSONKey :: ToJSONKeyFunction a
- toJSONKeyList :: ToJSONKeyFunction [a]
- data ToJSONKeyFunction a
- = ToJSONKeyText !(a -> Key) !(a -> Encoding' Key)
- | ToJSONKeyValue !(a -> Value) !(a -> Encoding)
- toJSONKeyText :: (a -> Text) -> ToJSONKeyFunction a
- toJSONKeyKey :: (a -> Key) -> ToJSONKeyFunction a
- contramapToJSONKeyFunction :: (b -> a) -> ToJSONKeyFunction a -> ToJSONKeyFunction b
- class GetConName f => GToJSONKey f
- genericToJSONKey :: (Generic a, GToJSONKey (Rep a)) => JSONKeyOptions -> ToJSONKeyFunction a
- class KeyValue kv where
- class Monoid kv => KeyValuePair v kv where
- class Monoid pairs => FromPairs enc pairs | enc -> pairs where
- fromPairs :: pairs -> enc
- listEncoding :: (a -> Encoding) -> [a] -> Encoding
- listValue :: (a -> Value) -> [a] -> Value
Core JSON classes
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 writeTextliterals. {-# LANGUAGE OverloadedStrings #-} data Coord = Coord { x :: Double, y :: Double } instanceToJSONCoord wheretoJSON(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 clause to your
datatype and declare a GenericToJSON 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=maptoUpper} instanceToJSONCoord wheretoJSON=genericToJSONcustomOptionstoEncoding=genericToEncodingcustomOptions
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
toJSONis directly serialized to aByteString. 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
toEncodingstill compile and have the correct semantics. This is ensured by making the default implementation oftoEncodingusetoJSON. This produces correct results, but since it performs an intermediate conversion to aValue, it will be less efficient than directly emitting anEncoding. (this also means that specifying nothing more thaninstance ToJSON Coordwould be sufficient as a generically decoding instance, but there probably exists no good reason to not specifytoEncodingin new instances.)
Minimal complete definition
Nothing
Methods
Convert a Haskell value to a JSON-friendly intermediate type.
toEncoding :: a -> Encoding Source #
Encode a Haskell value as JSON.
The default implementation of this method creates an
intermediate Value using toJSON. This provides
source-level compatibility for people upgrading from older
versions of this library, but obviously offers no performance
advantage.
To benefit from direct encoding, you must provide an
implementation for this method. The easiest way to do so is by
having your types implement Generic using the DeriveGeneric
extension, and then have GHC generate a method body as follows.
instanceToJSONCoord wheretoEncoding=genericToEncodingdefaultOptions
toJSONList :: [a] -> Value Source #
toEncodingList :: [a] -> Encoding Source #
Instances
Liftings to unary and binary type constructors
class ToJSON1 f where Source #
Lifting of the ToJSON class to unary type constructors.
Instead of manually writing your ToJSON1 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
toJSON1.
To use the second, simply add a deriving clause to your
datatype and declare a Generic1ToJSON1 instance for your datatype without giving
definitions for liftToJSON or liftToEncoding.
For example:
{-# LANGUAGE DeriveGeneric #-}
import GHC.Generics
data Pair a b = Pair { pairFst :: a, pairSnd :: b } deriving Generic1
instance ToJSON a => ToJSON1 (Pair a)
If the default implementation doesn't give exactly the results you want,
you can customize the generic encoding with only a tiny amount of
effort, using genericLiftToJSON and genericLiftToEncoding with
your preferred Options:
customOptions =defaultOptions{fieldLabelModifier=maptoUpper} instanceToJSONa =>ToJSON1(Pair a) whereliftToJSON=genericLiftToJSONcustomOptionsliftToEncoding=genericLiftToEncodingcustomOptions
See also ToJSON.
Minimal complete definition
Nothing
Methods
liftToJSON :: (a -> Value) -> ([a] -> Value) -> f a -> Value Source #
default liftToJSON :: (Generic1 f, GToJSON' Value One (Rep1 f)) => (a -> Value) -> ([a] -> Value) -> f a -> Value Source #
liftToJSONList :: (a -> Value) -> ([a] -> Value) -> [f a] -> Value Source #
liftToEncoding :: (a -> Encoding) -> ([a] -> Encoding) -> f a -> Encoding Source #
default liftToEncoding :: (Generic1 f, GToJSON' Encoding One (Rep1 f)) => (a -> Encoding) -> ([a] -> Encoding) -> f a -> Encoding Source #
liftToEncodingList :: (a -> Encoding) -> ([a] -> Encoding) -> [f a] -> Encoding Source #
Instances
toJSON1 :: (ToJSON1 f, ToJSON a) => f a -> Value Source #
Lift the standard toJSON function through the type constructor.
toEncoding1 :: (ToJSON1 f, ToJSON a) => f a -> Encoding Source #
Lift the standard toEncoding function through the type constructor.
class ToJSON2 f where Source #
Lifting of the ToJSON class to binary type constructors.
Instead of manually writing your ToJSON2 instance, Data.Aeson.TH
provides Template Haskell functions which will derive an instance at compile time.
The compiler cannot provide a default generic implementation for liftToJSON2,
unlike toJSON and liftToJSON.
Minimal complete definition
Methods
liftToJSON2 :: (a -> Value) -> ([a] -> Value) -> (b -> Value) -> ([b] -> Value) -> f a b -> Value Source #
liftToJSONList2 :: (a -> Value) -> ([a] -> Value) -> (b -> Value) -> ([b] -> Value) -> [f a b] -> Value Source #
liftToEncoding2 :: (a -> Encoding) -> ([a] -> Encoding) -> (b -> Encoding) -> ([b] -> Encoding) -> f a b -> Encoding Source #
liftToEncodingList2 :: (a -> Encoding) -> ([a] -> Encoding) -> (b -> Encoding) -> ([b] -> Encoding) -> [f a b] -> Encoding Source #
Instances
| ToJSON2 Either Source # | |
Defined in Data.Aeson.Types.ToJSON Methods liftToJSON2 :: (a -> Value) -> ([a] -> Value) -> (b -> Value) -> ([b] -> Value) -> Either a b -> Value Source # liftToJSONList2 :: (a -> Value) -> ([a] -> Value) -> (b -> Value) -> ([b] -> Value) -> [Either a b] -> Value Source # liftToEncoding2 :: (a -> Encoding) -> ([a] -> Encoding) -> (b -> Encoding) -> ([b] -> Encoding) -> Either a b -> Encoding Source # liftToEncodingList2 :: (a -> Encoding) -> ([a] -> Encoding) -> (b -> Encoding) -> ([b] -> Encoding) -> [Either a b] -> Encoding Source # | |
| ToJSON2 (,) Source # | |
Defined in Data.Aeson.Types.ToJSON Methods liftToJSON2 :: (a -> Value) -> ([a] -> Value) -> (b -> Value) -> ([b] -> Value) -> (a, b) -> Value Source # liftToJSONList2 :: (a -> Value) -> ([a] -> Value) -> (b -> Value) -> ([b] -> Value) -> [(a, b)] -> Value Source # liftToEncoding2 :: (a -> Encoding) -> ([a] -> Encoding) -> (b -> Encoding) -> ([b] -> Encoding) -> (a, b) -> Encoding Source # liftToEncodingList2 :: (a -> Encoding) -> ([a] -> Encoding) -> (b -> Encoding) -> ([b] -> Encoding) -> [(a, b)] -> Encoding Source # | |
| ToJSON2 These Source # | Since: 1.5.1.0 |
Defined in Data.Aeson.Types.ToJSON Methods liftToJSON2 :: (a -> Value) -> ([a] -> Value) -> (b -> Value) -> ([b] -> Value) -> These a b -> Value Source # liftToJSONList2 :: (a -> Value) -> ([a] -> Value) -> (b -> Value) -> ([b] -> Value) -> [These a b] -> Value Source # liftToEncoding2 :: (a -> Encoding) -> ([a] -> Encoding) -> (b -> Encoding) -> ([b] -> Encoding) -> These a b -> Encoding Source # liftToEncodingList2 :: (a -> Encoding) -> ([a] -> Encoding) -> (b -> Encoding) -> ([b] -> Encoding) -> [These a b] -> Encoding Source # | |
| ToJSON2 Pair Source # | Since: 1.5.3.0 |
Defined in Data.Aeson.Types.ToJSON Methods liftToJSON2 :: (a -> Value) -> ([a] -> Value) -> (b -> Value) -> ([b] -> Value) -> Pair a b -> Value Source # liftToJSONList2 :: (a -> Value) -> ([a] -> Value) -> (b -> Value) -> ([b] -> Value) -> [Pair a b] -> Value Source # liftToEncoding2 :: (a -> Encoding) -> ([a] -> Encoding) -> (b -> Encoding) -> ([b] -> Encoding) -> Pair a b -> Encoding Source # liftToEncodingList2 :: (a -> Encoding) -> ([a] -> Encoding) -> (b -> Encoding) -> ([b] -> Encoding) -> [Pair a b] -> Encoding Source # | |
| ToJSON2 These Source # | Since: 1.5.3.0 |
Defined in Data.Aeson.Types.ToJSON Methods liftToJSON2 :: (a -> Value) -> ([a] -> Value) -> (b -> Value) -> ([b] -> Value) -> These a b -> Value Source # liftToJSONList2 :: (a -> Value) -> ([a] -> Value) -> (b -> Value) -> ([b] -> Value) -> [These a b] -> Value Source # liftToEncoding2 :: (a -> Encoding) -> ([a] -> Encoding) -> (b -> Encoding) -> ([b] -> Encoding) -> These a b -> Encoding Source # liftToEncodingList2 :: (a -> Encoding) -> ([a] -> Encoding) -> (b -> Encoding) -> ([b] -> Encoding) -> [These a b] -> Encoding Source # | |
| ToJSON2 Either Source # | Since: 1.5.3.0 |
Defined in Data.Aeson.Types.ToJSON Methods liftToJSON2 :: (a -> Value) -> ([a] -> Value) -> (b -> Value) -> ([b] -> Value) -> Either a b -> Value Source # liftToJSONList2 :: (a -> Value) -> ([a] -> Value) -> (b -> Value) -> ([b] -> Value) -> [Either a b] -> Value Source # liftToEncoding2 :: (a -> Encoding) -> ([a] -> Encoding) -> (b -> Encoding) -> ([b] -> Encoding) -> Either a b -> Encoding Source # liftToEncodingList2 :: (a -> Encoding) -> ([a] -> Encoding) -> (b -> Encoding) -> ([b] -> Encoding) -> [Either a b] -> Encoding Source # | |
| ToJSON a => ToJSON2 ((,,) a) Source # | |
Defined in Data.Aeson.Types.ToJSON Methods liftToJSON2 :: (a0 -> Value) -> ([a0] -> Value) -> (b -> Value) -> ([b] -> Value) -> (a, a0, b) -> Value Source # liftToJSONList2 :: (a0 -> Value) -> ([a0] -> Value) -> (b -> Value) -> ([b] -> Value) -> [(a, a0, b)] -> Value Source # liftToEncoding2 :: (a0 -> Encoding) -> ([a0] -> Encoding) -> (b -> Encoding) -> ([b] -> Encoding) -> (a, a0, b) -> Encoding Source # liftToEncodingList2 :: (a0 -> Encoding) -> ([a0] -> Encoding) -> (b -> Encoding) -> ([b] -> Encoding) -> [(a, a0, b)] -> Encoding Source # | |
| ToJSON2 (Const :: Type -> Type -> Type) Source # | |
Defined in Data.Aeson.Types.ToJSON Methods liftToJSON2 :: (a -> Value) -> ([a] -> Value) -> (b -> Value) -> ([b] -> Value) -> Const a b -> Value Source # liftToJSONList2 :: (a -> Value) -> ([a] -> Value) -> (b -> Value) -> ([b] -> Value) -> [Const a b] -> Value Source # liftToEncoding2 :: (a -> Encoding) -> ([a] -> Encoding) -> (b -> Encoding) -> ([b] -> Encoding) -> Const a b -> Encoding Source # liftToEncodingList2 :: (a -> Encoding) -> ([a] -> Encoding) -> (b -> Encoding) -> ([b] -> Encoding) -> [Const a b] -> Encoding Source # | |
| ToJSON2 (Tagged :: Type -> Type -> Type) Source # | |
Defined in Data.Aeson.Types.ToJSON Methods liftToJSON2 :: (a -> Value) -> ([a] -> Value) -> (b -> Value) -> ([b] -> Value) -> Tagged a b -> Value Source # liftToJSONList2 :: (a -> Value) -> ([a] -> Value) -> (b -> Value) -> ([b] -> Value) -> [Tagged a b] -> Value Source # liftToEncoding2 :: (a -> Encoding) -> ([a] -> Encoding) -> (b -> Encoding) -> ([b] -> Encoding) -> Tagged a b -> Encoding Source # liftToEncodingList2 :: (a -> Encoding) -> ([a] -> Encoding) -> (b -> Encoding) -> ([b] -> Encoding) -> [Tagged a b] -> Encoding Source # | |
| (ToJSON a, ToJSON b) => ToJSON2 ((,,,) a b) Source # | |
Defined in Data.Aeson.Types.ToJSON Methods liftToJSON2 :: (a0 -> Value) -> ([a0] -> Value) -> (b0 -> Value) -> ([b0] -> Value) -> (a, b, a0, b0) -> Value Source # liftToJSONList2 :: (a0 -> Value) -> ([a0] -> Value) -> (b0 -> Value) -> ([b0] -> Value) -> [(a, b, a0, b0)] -> Value Source # liftToEncoding2 :: (a0 -> Encoding) -> ([a0] -> Encoding) -> (b0 -> Encoding) -> ([b0] -> Encoding) -> (a, b, a0, b0) -> Encoding Source # liftToEncodingList2 :: (a0 -> Encoding) -> ([a0] -> Encoding) -> (b0 -> Encoding) -> ([b0] -> Encoding) -> [(a, b, a0, b0)] -> Encoding Source # | |
| (ToJSON a, ToJSON b, ToJSON c) => ToJSON2 ((,,,,) a b c) Source # | |
Defined in Data.Aeson.Types.ToJSON Methods liftToJSON2 :: (a0 -> Value) -> ([a0] -> Value) -> (b0 -> Value) -> ([b0] -> Value) -> (a, b, c, a0, b0) -> Value Source # liftToJSONList2 :: (a0 -> Value) -> ([a0] -> Value) -> (b0 -> Value) -> ([b0] -> Value) -> [(a, b, c, a0, b0)] -> Value Source # liftToEncoding2 :: (a0 -> Encoding) -> ([a0] -> Encoding) -> (b0 -> Encoding) -> ([b0] -> Encoding) -> (a, b, c, a0, b0) -> Encoding Source # liftToEncodingList2 :: (a0 -> Encoding) -> ([a0] -> Encoding) -> (b0 -> Encoding) -> ([b0] -> Encoding) -> [(a, b, c, a0, b0)] -> Encoding Source # | |
| (ToJSON a, ToJSON b, ToJSON c, ToJSON d) => ToJSON2 ((,,,,,) a b c d) Source # | |
Defined in Data.Aeson.Types.ToJSON Methods liftToJSON2 :: (a0 -> Value) -> ([a0] -> Value) -> (b0 -> Value) -> ([b0] -> Value) -> (a, b, c, d, a0, b0) -> Value Source # liftToJSONList2 :: (a0 -> Value) -> ([a0] -> Value) -> (b0 -> Value) -> ([b0] -> Value) -> [(a, b, c, d, a0, b0)] -> Value Source # liftToEncoding2 :: (a0 -> Encoding) -> ([a0] -> Encoding) -> (b0 -> Encoding) -> ([b0] -> Encoding) -> (a, b, c, d, a0, b0) -> Encoding Source # liftToEncodingList2 :: (a0 -> Encoding) -> ([a0] -> Encoding) -> (b0 -> Encoding) -> ([b0] -> Encoding) -> [(a, b, c, d, a0, b0)] -> Encoding Source # | |
| (ToJSON a, ToJSON b, ToJSON c, ToJSON d, ToJSON e) => ToJSON2 ((,,,,,,) a b c d e) Source # | |
Defined in Data.Aeson.Types.ToJSON Methods liftToJSON2 :: (a0 -> Value) -> ([a0] -> Value) -> (b0 -> Value) -> ([b0] -> Value) -> (a, b, c, d, e, a0, b0) -> Value Source # liftToJSONList2 :: (a0 -> Value) -> ([a0] -> Value) -> (b0 -> Value) -> ([b0] -> Value) -> [(a, b, c, d, e, a0, b0)] -> Value Source # liftToEncoding2 :: (a0 -> Encoding) -> ([a0] -> Encoding) -> (b0 -> Encoding) -> ([b0] -> Encoding) -> (a, b, c, d, e, a0, b0) -> Encoding Source # liftToEncodingList2 :: (a0 -> Encoding) -> ([a0] -> Encoding) -> (b0 -> Encoding) -> ([b0] -> Encoding) -> [(a, b, c, d, e, a0, b0)] -> Encoding Source # | |
| (ToJSON a, ToJSON b, ToJSON c, ToJSON d, ToJSON e, ToJSON f) => ToJSON2 ((,,,,,,,) a b c d e f) Source # | |
Defined in Data.Aeson.Types.ToJSON Methods liftToJSON2 :: (a0 -> Value) -> ([a0] -> Value) -> (b0 -> Value) -> ([b0] -> Value) -> (a, b, c, d, e, f, a0, b0) -> Value Source # liftToJSONList2 :: (a0 -> Value) -> ([a0] -> Value) -> (b0 -> Value) -> ([b0] -> Value) -> [(a, b, c, d, e, f, a0, b0)] -> Value Source # liftToEncoding2 :: (a0 -> Encoding) -> ([a0] -> Encoding) -> (b0 -> Encoding) -> ([b0] -> Encoding) -> (a, b, c, d, e, f, a0, b0) -> Encoding Source # liftToEncodingList2 :: (a0 -> Encoding) -> ([a0] -> Encoding) -> (b0 -> Encoding) -> ([b0] -> Encoding) -> [(a, b, c, d, e, f, a0, b0)] -> Encoding Source # | |
| (ToJSON a, ToJSON b, ToJSON c, ToJSON d, ToJSON e, ToJSON f, ToJSON g) => ToJSON2 ((,,,,,,,,) a b c d e f g) Source # | |
Defined in Data.Aeson.Types.ToJSON Methods liftToJSON2 :: (a0 -> Value) -> ([a0] -> Value) -> (b0 -> Value) -> ([b0] -> Value) -> (a, b, c, d, e, f, g, a0, b0) -> Value Source # liftToJSONList2 :: (a0 -> Value) -> ([a0] -> Value) -> (b0 -> Value) -> ([b0] -> Value) -> [(a, b, c, d, e, f, g, a0, b0)] -> Value Source # liftToEncoding2 :: (a0 -> Encoding) -> ([a0] -> Encoding) -> (b0 -> Encoding) -> ([b0] -> Encoding) -> (a, b, c, d, e, f, g, a0, b0) -> Encoding Source # liftToEncodingList2 :: (a0 -> Encoding) -> ([a0] -> Encoding) -> (b0 -> Encoding) -> ([b0] -> Encoding) -> [(a, b, c, d, e, f, g, a0, b0)] -> Encoding Source # | |
| (ToJSON a, ToJSON b, ToJSON c, ToJSON d, ToJSON e, ToJSON f, ToJSON g, ToJSON h) => ToJSON2 ((,,,,,,,,,) a b c d e f g h) Source # | |
Defined in Data.Aeson.Types.ToJSON Methods liftToJSON2 :: (a0 -> Value) -> ([a0] -> Value) -> (b0 -> Value) -> ([b0] -> Value) -> (a, b, c, d, e, f, g, h, a0, b0) -> Value Source # liftToJSONList2 :: (a0 -> Value) -> ([a0] -> Value) -> (b0 -> Value) -> ([b0] -> Value) -> [(a, b, c, d, e, f, g, h, a0, b0)] -> Value Source # liftToEncoding2 :: (a0 -> Encoding) -> ([a0] -> Encoding) -> (b0 -> Encoding) -> ([b0] -> Encoding) -> (a, b, c, d, e, f, g, h, a0, b0) -> Encoding Source # liftToEncodingList2 :: (a0 -> Encoding) -> ([a0] -> Encoding) -> (b0 -> Encoding) -> ([b0] -> Encoding) -> [(a, b, c, d, e, f, g, h, a0, b0)] -> Encoding Source # | |
| (ToJSON a, ToJSON b, ToJSON c, ToJSON d, ToJSON e, ToJSON f, ToJSON g, ToJSON h, ToJSON i) => ToJSON2 ((,,,,,,,,,,) a b c d e f g h i) Source # | |
Defined in Data.Aeson.Types.ToJSON Methods liftToJSON2 :: (a0 -> Value) -> ([a0] -> Value) -> (b0 -> Value) -> ([b0] -> Value) -> (a, b, c, d, e, f, g, h, i, a0, b0) -> Value Source # liftToJSONList2 :: (a0 -> Value) -> ([a0] -> Value) -> (b0 -> Value) -> ([b0] -> Value) -> [(a, b, c, d, e, f, g, h, i, a0, b0)] -> Value Source # liftToEncoding2 :: (a0 -> Encoding) -> ([a0] -> Encoding) -> (b0 -> Encoding) -> ([b0] -> Encoding) -> (a, b, c, d, e, f, g, h, i, a0, b0) -> Encoding Source # liftToEncodingList2 :: (a0 -> Encoding) -> ([a0] -> Encoding) -> (b0 -> Encoding) -> ([b0] -> Encoding) -> [(a, b, c, d, e, f, g, h, i, a0, b0)] -> Encoding Source # | |
| (ToJSON a, ToJSON b, ToJSON c, ToJSON d, ToJSON e, ToJSON f, ToJSON g, ToJSON h, ToJSON i, ToJSON j) => ToJSON2 ((,,,,,,,,,,,) a b c d e f g h i j) Source # | |
Defined in Data.Aeson.Types.ToJSON Methods liftToJSON2 :: (a0 -> Value) -> ([a0] -> Value) -> (b0 -> Value) -> ([b0] -> Value) -> (a, b, c, d, e, f, g, h, i, j, a0, b0) -> Value Source # liftToJSONList2 :: (a0 -> Value) -> ([a0] -> Value) -> (b0 -> Value) -> ([b0] -> Value) -> [(a, b, c, d, e, f, g, h, i, j, a0, b0)] -> Value Source # liftToEncoding2 :: (a0 -> Encoding) -> ([a0] -> Encoding) -> (b0 -> Encoding) -> ([b0] -> Encoding) -> (a, b, c, d, e, f, g, h, i, j, a0, b0) -> Encoding Source # liftToEncodingList2 :: (a0 -> Encoding) -> ([a0] -> Encoding) -> (b0 -> Encoding) -> ([b0] -> Encoding) -> [(a, b, c, d, e, f, g, h, i, j, a0, b0)] -> Encoding Source # | |
| (ToJSON a, ToJSON b, ToJSON c, ToJSON d, ToJSON e, ToJSON f, ToJSON g, ToJSON h, ToJSON i, ToJSON j, ToJSON k) => ToJSON2 ((,,,,,,,,,,,,) a b c d e f g h i j k) Source # | |
Defined in Data.Aeson.Types.ToJSON Methods liftToJSON2 :: (a0 -> Value) -> ([a0] -> Value) -> (b0 -> Value) -> ([b0] -> Value) -> (a, b, c, d, e, f, g, h, i, j, k, a0, b0) -> Value Source # liftToJSONList2 :: (a0 -> Value) -> ([a0] -> Value) -> (b0 -> Value) -> ([b0] -> Value) -> [(a, b, c, d, e, f, g, h, i, j, k, a0, b0)] -> Value Source # liftToEncoding2 :: (a0 -> Encoding) -> ([a0] -> Encoding) -> (b0 -> Encoding) -> ([b0] -> Encoding) -> (a, b, c, d, e, f, g, h, i, j, k, a0, b0) -> Encoding Source # liftToEncodingList2 :: (a0 -> Encoding) -> ([a0] -> Encoding) -> (b0 -> Encoding) -> ([b0] -> Encoding) -> [(a, b, c, d, e, f, g, h, i, j, k, a0, b0)] -> Encoding Source # | |
| (ToJSON a, ToJSON b, ToJSON c, ToJSON d, ToJSON e, ToJSON f, ToJSON g, ToJSON h, ToJSON i, ToJSON j, ToJSON k, ToJSON l) => ToJSON2 ((,,,,,,,,,,,,,) a b c d e f g h i j k l) Source # | |
Defined in Data.Aeson.Types.ToJSON Methods liftToJSON2 :: (a0 -> Value) -> ([a0] -> Value) -> (b0 -> Value) -> ([b0] -> Value) -> (a, b, c, d, e, f, g, h, i, j, k, l, a0, b0) -> Value Source # liftToJSONList2 :: (a0 -> Value) -> ([a0] -> Value) -> (b0 -> Value) -> ([b0] -> Value) -> [(a, b, c, d, e, f, g, h, i, j, k, l, a0, b0)] -> Value Source # liftToEncoding2 :: (a0 -> Encoding) -> ([a0] -> Encoding) -> (b0 -> Encoding) -> ([b0] -> Encoding) -> (a, b, c, d, e, f, g, h, i, j, k, l, a0, b0) -> Encoding Source # liftToEncodingList2 :: (a0 -> Encoding) -> ([a0] -> Encoding) -> (b0 -> Encoding) -> ([b0] -> Encoding) -> [(a, b, c, d, e, f, g, h, i, j, k, l, a0, b0)] -> Encoding Source # | |
| (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) => ToJSON2 ((,,,,,,,,,,,,,,) a b c d e f g h i j k l m) Source # | |
Defined in Data.Aeson.Types.ToJSON Methods liftToJSON2 :: (a0 -> Value) -> ([a0] -> Value) -> (b0 -> Value) -> ([b0] -> Value) -> (a, b, c, d, e, f, g, h, i, j, k, l, m, a0, b0) -> Value Source # liftToJSONList2 :: (a0 -> Value) -> ([a0] -> Value) -> (b0 -> Value) -> ([b0] -> Value) -> [(a, b, c, d, e, f, g, h, i, j, k, l, m, a0, b0)] -> Value Source # liftToEncoding2 :: (a0 -> Encoding) -> ([a0] -> Encoding) -> (b0 -> Encoding) -> ([b0] -> Encoding) -> (a, b, c, d, e, f, g, h, i, j, k, l, m, a0, b0) -> Encoding Source # liftToEncodingList2 :: (a0 -> Encoding) -> ([a0] -> Encoding) -> (b0 -> Encoding) -> ([b0] -> Encoding) -> [(a, b, c, d, e, f, g, h, i, j, k, l, m, a0, b0)] -> Encoding Source # | |
toJSON2 :: (ToJSON2 f, ToJSON a, ToJSON b) => f a b -> Value Source #
Lift the standard toJSON function through the type constructor.
toEncoding2 :: (ToJSON2 f, ToJSON a, ToJSON b) => f a b -> Encoding Source #
Lift the standard toEncoding function through the type constructor.
Generic JSON classes
class GToJSON' enc arity f where Source #
Class of generic representation types that can be converted to JSON.
Methods
gToJSON :: Options -> ToArgs enc arity a -> f a -> enc Source #
This method (applied to defaultOptions) is used as the
default generic implementation of toJSON
(with enc ~ and Valuearity ~ )
and ZeroliftToJSON (if the arity is One).
It also provides a generic implementation of toEncoding
(with enc ~ and Encodingarity ~ )
and ZeroliftToEncoding (if the arity is One).
Instances
| GToJSON' enc One Par1 Source # | |
| GToJSON' Value arity (U1 :: Type -> Type) Source # | |
| GToJSON' Value arity (V1 :: Type -> Type) Source # | |
| GToJSON' Encoding arity (U1 :: Type -> Type) Source # | |
| ToJSON1 f => GToJSON' Value One (Rec1 f) Source # | |
| ToJSON1 f => GToJSON' Encoding One (Rec1 f) Source # | |
| (AllNullary (a :+: b) allNullary, SumToJSON enc arity (a :+: b) allNullary) => GToJSON' enc arity (a :+: b) Source # | |
| ConsToJSON enc arity a => GToJSON' enc arity (C1 c a) Source # | |
| (ConsToJSON enc arity a, AllNullary (C1 c a) allNullary, SumToJSON enc arity (C1 c a) allNullary) => GToJSON' enc arity (D1 d (C1 c a)) Source # | |
| (WriteProduct arity a, WriteProduct arity b, ProductSize a, ProductSize b) => GToJSON' Value arity (a :*: b) Source # | |
| ToJSON a => GToJSON' Value arity (K1 i a :: Type -> Type) Source # | |
| (EncodeProduct arity a, EncodeProduct arity b) => GToJSON' Encoding arity (a :*: b) Source # | |
| ToJSON a => GToJSON' Encoding arity (K1 i a :: Type -> Type) Source # | |
| GToJSON' enc arity a => GToJSON' enc arity (M1 i c a) Source # | |
| (ToJSON1 f, GToJSON' Value One g) => GToJSON' Value One (f :.: g) Source # | |
| (ToJSON1 f, GToJSON' Encoding One g) => GToJSON' Encoding One (f :.: g) Source # | |
genericToJSON :: (Generic a, GToJSON' Value Zero (Rep a)) => Options -> a -> Value Source #
A configurable generic JSON creator. This function applied to
defaultOptions is used as the default for toJSON when the type
is an instance of Generic.
genericToEncoding :: (Generic a, GToJSON' Encoding Zero (Rep a)) => Options -> a -> Encoding Source #
A configurable generic JSON encoder. This function applied to
defaultOptions is used as the default for toEncoding when the type
is an instance of Generic.
genericLiftToJSON :: (Generic1 f, GToJSON' Value One (Rep1 f)) => Options -> (a -> Value) -> ([a] -> Value) -> f a -> Value Source #
A configurable generic JSON creator. This function applied to
defaultOptions is used as the default for liftToJSON when the type
is an instance of Generic1.
genericLiftToEncoding :: (Generic1 f, GToJSON' Encoding One (Rep1 f)) => Options -> (a -> Encoding) -> ([a] -> Encoding) -> f a -> Encoding Source #
A configurable generic JSON encoder. This function applied to
defaultOptions is used as the default for liftToEncoding when the type
is an instance of Generic1.
Classes and types for map keys
class ToJSONKey a where Source #
Typeclass for types that can be used as the key of a map-like container
(like Map or HashMap). For example, since Text has a ToJSONKey
instance and Char has a ToJSON instance, we can encode a value of
type Map Text Char:
>>>LBC8.putStrLn $ encode $ Map.fromList [("foo" :: Text, 'a')]{"foo":"a"}
Since Int also has a ToJSONKey instance, we can similarly write:
>>>LBC8.putStrLn $ encode $ Map.fromList [(5 :: Int, 'a')]{"5":"a"}
JSON documents only accept strings as object keys. For any type
from base that has a natural textual representation, it can be
expected that its ToJSONKey instance will choose that representation.
For data types that lack a natural textual representation, an alternative is provided. The map-like container is represented as a JSON array instead of a JSON object. Each value in the array is an array with exactly two values. The first is the key and the second is the value.
For example, values of type '[Text]' cannot be encoded to a
string, so a Map with keys of type '[Text]' is encoded as follows:
>>>LBC8.putStrLn $ encode $ Map.fromList [(["foo","bar","baz" :: Text], 'a')][[["foo","bar","baz"],"a"]]
The default implementation of ToJSONKey chooses this method of
encoding a key, using the ToJSON instance of the type.
To use your own data type as the key in a map, all that is needed
is to write a ToJSONKey (and possibly a FromJSONKey) instance
for it. If the type cannot be trivially converted to and from Text,
it is recommended that ToJSONKeyValue is used. Since the default
implementations of the typeclass methods can build this from a
ToJSON instance, there is nothing that needs to be written:
data Foo = Foo { fooAge :: Int, fooName :: Text }
deriving (Eq,Ord,Generic)
instance ToJSON Foo
instance ToJSONKey FooThat's it. We can now write:
>>>let m = Map.fromList [(Foo 4 "bar",'a'),(Foo 6 "arg",'b')]>>>LBC8.putStrLn $ encode m[[{"fooName":"bar","fooAge":4},"a"],[{"fooName":"arg","fooAge":6},"b"]]
The next case to consider is if we have a type that is a
newtype wrapper around Text. The recommended approach is to use
generalized newtype deriving:
newtype RecordId = RecordId { getRecordId :: Text }
deriving (Eq,Ord,ToJSONKey)Then we may write:
>>>LBC8.putStrLn $ encode $ Map.fromList [(RecordId "abc",'a')]{"abc":"a"}
Simple sum types are a final case worth considering. Suppose we have:
data Color = Red | Green | Blue deriving (Show,Read,Eq,Ord)
It is possible to get the ToJSONKey instance for free as we did
with Foo. However, in this case, we have a natural way to go to
and from Text that does not require any escape sequences. So
ToJSONKeyText can be used instead of ToJSONKeyValue to encode maps
as objects instead of arrays of pairs. This instance may be
implemented using generics as follows:
instanceToJSONKeyColor wheretoJSONKey=genericToJSONKeydefaultJSONKeyOptions
Low-level implementations
The Show instance can be used to help write ToJSONKey:
instance ToJSONKey Color where
toJSONKey = ToJSONKeyText f g
where f = Text.pack . show
g = text . Text.pack . show
-- text function is from Data.Aeson.EncodingThe situation of needing to turning function a -> Text into
a ToJSONKeyFunction is common enough that a special combinator
is provided for it. The above instance can be rewritten as:
instance ToJSONKey Color where toJSONKey = toJSONKeyText (Text.pack . show)
The performance of the above instance can be improved by
not using String as an intermediate step when converting to
Text. One option for improving performance would be to use
template haskell machinery from the text-show package. However,
even with the approach, the Encoding (a wrapper around a bytestring
builder) is generated by encoding the Text to a ByteString,
an intermediate step that could be avoided. The fastest possible
implementation would be:
-- Assuming that OverloadedStrings is enabled
instance ToJSONKey Color where
toJSONKey = ToJSONKeyText f g
where f x = case x of {Red -> "Red";Green ->"Green";Blue -> "Blue"}
g x = case x of {Red -> text "Red";Green -> text "Green";Blue -> text "Blue"}
-- text function is from Data.Aeson.EncodingThis works because GHC can lift the encoded values out of the case statements, which means that they are only evaluated once. This approach should only be used when there is a serious need to maximize performance.
Minimal complete definition
Nothing
Methods
toJSONKey :: ToJSONKeyFunction a Source #
Strategy for rendering the key for a map-like container.
default toJSONKey :: ToJSON a => ToJSONKeyFunction a Source #
toJSONKeyList :: ToJSONKeyFunction [a] Source #
This is similar in spirit to the showsList method of Show.
It makes it possible to give String keys special treatment
without using OverlappingInstances. End users should always
be able to use the default implementation of this method.
default toJSONKeyList :: ToJSON a => ToJSONKeyFunction [a] Source #
Instances
data ToJSONKeyFunction a Source #
Constructors
| ToJSONKeyText !(a -> Key) !(a -> Encoding' Key) | key is encoded to string, produces object |
| ToJSONKeyValue !(a -> Value) !(a -> Encoding) | key is encoded to value, produces array |
Instances
| Contravariant ToJSONKeyFunction Source # | |
Defined in Data.Aeson.Types.ToJSON Methods contramap :: (a -> b) -> ToJSONKeyFunction b -> ToJSONKeyFunction a Source # (>$) :: b -> ToJSONKeyFunction b -> ToJSONKeyFunction a Source # | |
toJSONKeyText :: (a -> Text) -> ToJSONKeyFunction a Source #
Helper for creating textual keys.
instanceToJSONKeyMyKey wheretoJSONKey=toJSONKeyTextmyKeyToText where myKeyToText = Text.pack . show -- or showt from text-show
toJSONKeyKey :: (a -> Key) -> ToJSONKeyFunction a Source #
Since: 2.0.0.0
contramapToJSONKeyFunction :: (b -> a) -> ToJSONKeyFunction a -> ToJSONKeyFunction b Source #
Contravariant map, as ToJSONKeyFunction is a contravariant functor.
class GetConName f => GToJSONKey f Source #
Instances
| GetConName f => GToJSONKey (f :: k -> Type) Source # | |
Defined in Data.Aeson.Types.ToJSON | |
genericToJSONKey :: (Generic a, GToJSONKey (Rep a)) => JSONKeyOptions -> ToJSONKeyFunction a Source #
Object key-value pairs
class KeyValue kv where Source #
A key-value pair for encoding a JSON object.
class Monoid kv => KeyValuePair v kv where Source #
class Monoid pairs => FromPairs enc pairs | enc -> pairs where Source #
Wrap a list of pairs as an object.
Functions needed for documentation
Encoding functions
listEncoding :: (a -> Encoding) -> [a] -> Encoding Source #
Helper function to use with liftToEncoding.
Useful when writing own ToJSON1 instances.
newtype F a = F [a] -- This instance encodesStringas an array of chars instanceToJSON1F whereliftToJSONtj _ (F xs) =liftToJSONtj (listValuetj) xsliftToEncodingte _ (F xs) =liftToEncodingte (listEncodingte) xs instanceFromJSON1F whereliftParseJSONp _ v = F <$>liftParseJSONp (listParserp) v
listValue :: (a -> Value) -> [a] -> Value Source #
Helper function to use with liftToJSON, see listEncoding.