Generics.SOP.JSON

Configuration

type JsonFieldName = String

type JsonTagName = String

data JsonOptions

JSON encoder/decoder configuration

Constructors

JsonOptions

Fields

jsonFieldName :: DatatypeName -> FieldName -> JsonFieldName

Construct the name for JSON object fields (not for the tags that are used for sum-types, however)

The default just uses the name of the corresponding Haskell constructor

jsonTagName :: ConstructorName -> JsonTagName

Construct the name for a tag for sum-types.

The default just uses the name of the Haskell constructor.

Instances

Typeable * JsonOptions

defaultJsonOptions :: JsonOptions

JSON view of a datatype

data Tag

Constructor tag

For a datatype with a single constructor we do not need to tag values with their constructor; but for a datatype with multiple constructors we do.

Constructors

NoTag

Tag JsonTagName

Instances

Typeable * Tag

data JsonInfo :: [*] -> * where

Constructors

JsonZero :: ConstructorName -> JsonInfo []

JsonOne :: Tag -> JsonInfo `[a]`

JsonMultiple :: SingI xs => Tag -> JsonInfo xs

JsonRecord :: SingI xs => Tag -> NP (K String) xs -> JsonInfo xs

Instances

Typeable ([*] -> *) JsonInfo

jsonInfo :: forall a. (HasDatatypeInfo a, SingI (Code a)) => Proxy a -> JsonOptions -> NP JsonInfo (Code a)

Generic functions

gtoJSON :: forall a. (Generic a, HasDatatypeInfo a, All2 ToJSON (Code a)) => JsonOptions -> a -> Value

gparseJSON :: forall a. (Generic a, HasDatatypeInfo a, All2 FromJSON (Code a)) => JsonOptions -> Value -> Parser a

UpdateFromJSON and co

class UpdateFromJSON a where

For some values we can support "updating" the value with a "partial" JSON value; record types are the prime example (and the only one supported by the generic function). For non-record types we typically can only replace the value with a "complete" JSON value; in this case, we simply ignore the old value (see replaceWithJSON). Typical class instances will look like

instance UpdateFromJSON SomeRecordType where
   updateFromJSON = gupdateFromJSON <jsonOptions>

or

instance UpdateFromJSON SomeNonRecordType where
   updateFromJSON = replaceWithJSON

NOTE: The generic function uses one-level lenses for the object fields. We could generalize this to arbitrary paths, but then the type would change to

updateFromJSON :: Value -> Parser (a -> UpdateM a)

I.e., updating a value from JSON would, in general, involve a database write.

Methods

updateFromJSON :: Value -> Parser (a -> a)

Instances

UpdateFromJSON Bool

UpdateFromJSON Double

UpdateFromJSON Int

UpdateFromJSON Rational

UpdateFromJSON String

UpdateFromJSON Text.Text

FromJSON a => UpdateFromJSON [a]

FromJSON a => UpdateFromJSON (Maybe a)

Typeable (* -> Constraint) UpdateFromJSON

gupdateFromJSON :: forall a xs. (Generic a, HasDatatypeInfo a, All UpdateFromJSON xs, Code a ~ `[xs]`) => JsonOptions -> Value -> Parser (a -> a)

Construct a function that updates a value of some record type, given a JSON object with new values for some (or none, or all) of the fields

replaceWithJSON :: FromJSON a => Value -> Parser (a -> a)

For types that we can only replace "whole", rather than update field by field

parseWith :: UpdateFromJSON a => a -> Value -> Parser a

Conversely, for types that we can only parse if we have a starting point

Re-exports

class ToJSON a where

A type that can be converted to JSON.

An example type and instance:

@{-# LANGUAGE OverloadedStrings #-}

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

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

Note the use of the OverloadedStrings language extension which enables Text values to be written as string literals.

Instead of manually writing your ToJSON instance, there are three 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 will probably be more efficient than the following two options:
• Data.Aeson.Generic provides a generic toJSON function that accepts any type which is an instance of Data.
• If your compiler has support for the DeriveGeneric and DefaultSignatures language extensions (GHC 7.2 and newer), toJSON will have a default generic implementation.

To use the latter option, simply add a deriving Generic clause to your datatype and declare a ToJSON instance for your datatype without giving a definition for toJSON.

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 ToJSON Coord @

Note that, instead of using DefaultSignatures, it's also possible to parameterize the generic encoding using genericToJSON applied to your encoding/decoding Options:

instance ToJSON Coord where
    toJSON = genericToJSON defaultOptions

Minimal complete definition

Nothing

Methods

toJSON :: a -> Value

Instances

ToJSON Bool

ToJSON Char

ToJSON Double

ToJSON Float

ToJSON Int

ToJSON Int8

ToJSON Int16

ToJSON Int32

ToJSON Int64

ToJSON Integer

ToJSON Word

ToJSON Word8

ToJSON Word16

ToJSON Word32

ToJSON Word64

ToJSON ()

ToJSON Scientific

ToJSON Number

ToJSON Text.Text

ToJSON UTCTime

ToJSON Value

ToJSON DotNetTime

ToJSON IntSet

ToJSON Text

ToJSON ZonedTime

ToJSON [Char]

ToJSON a => ToJSON [a]

ToJSON (Ratio Integer)

ToJSON a => ToJSON (Maybe a)

HasResolution a => ToJSON (Fixed a)

ToJSON a => ToJSON (Dual a)

ToJSON a => ToJSON (First a)

ToJSON a => ToJSON (Last a)

ToJSON a => ToJSON (IntMap a)

ToJSON a => ToJSON (Set a)

ToJSON v => ToJSON (Tree v)

ToJSON a => ToJSON (HashSet a)

ToJSON a => ToJSON (Vector.Vector a)

(Vector Vector a, ToJSON a) => ToJSON (Vector a)

(Storable a, ToJSON a) => ToJSON (Vector a)

(Prim a, ToJSON a) => ToJSON (Vector a)

(ToJSON a, ToJSON b) => ToJSON (Either a b)

(ToJSON a, ToJSON b) => ToJSON (a, b)

ToJSON v => ToJSON (HashMap.HashMap String v)

ToJSON v => ToJSON (HashMap.HashMap Text.Text v)

ToJSON v => ToJSON (HashMap.HashMap Text v)

ToJSON v => ToJSON (Map String v)

ToJSON v => ToJSON (Map Text.Text v)

ToJSON v => ToJSON (Map Text v)

(ToJSON a, ToJSON b, ToJSON c) => ToJSON (a, b, c)

(ToJSON a, ToJSON b, ToJSON c, ToJSON d) => ToJSON (a, b, c, d)

(ToJSON a, ToJSON b, ToJSON c, ToJSON d, ToJSON e) => ToJSON (a, b, c, d, e)

(ToJSON a, ToJSON b, ToJSON c, ToJSON d, ToJSON e, ToJSON f) => ToJSON (a, b, c, d, e, f)

(ToJSON a, ToJSON b, ToJSON c, ToJSON d, ToJSON e, ToJSON f, ToJSON g) => ToJSON (a, b, c, d, e, f, g)

(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)

(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)

(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)

(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)

(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)

(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)

(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)

(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)

class FromJSON a where

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

When writing an instance, use empty, mzero, or fail to make a conversion fail, e.g. if an Object is missing a required key, or the value is of the wrong type.

An example type and instance:

@{-# LANGUAGE OverloadedStrings #-}

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

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

-- A non-Object value is of the wrong type, so use mzero to fail. parseJSON _ = mzero @

Note the use of the OverloadedStrings language extension which enables Text values to be written as string literals.

Instead of manually writing your FromJSON instance, there are three 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 will probably be more efficient than the following two options:
• Data.Aeson.Generic provides a generic fromJSON function that parses to any type which is an instance of Data.
• If your compiler has support for the DeriveGeneric and DefaultSignatures language extensions, parseJSON will have a default generic implementation.

To use this, 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 @

Note that, instead of using DefaultSignatures, it's also possible to parameterize the generic decoding using genericParseJSON applied to your encoding/decoding Options:

instance FromJSON Coord where
    parseJSON = genericParseJSON defaultOptions

Minimal complete definition

Nothing

Methods

parseJSON :: Value -> Parser a

Instances

FromJSON Bool

FromJSON Char

FromJSON Double

FromJSON Float

FromJSON Int

FromJSON Int8

FromJSON Int16

FromJSON Int32

FromJSON Int64

FromJSON Integer

WARNING: Only parse Integers from trusted input since an attacker could easily fill up the memory of the target system by specifying a scientific number with a big exponent like 1e1000000000.

FromJSON Word

FromJSON Word8

FromJSON Word16

FromJSON Word32

FromJSON Word64

FromJSON ()

FromJSON Scientific

FromJSON Number

FromJSON Text.Text

FromJSON UTCTime

FromJSON Value

FromJSON DotNetTime

FromJSON IntSet

FromJSON Text

FromJSON ZonedTime

FromJSON [Char]

FromJSON a => FromJSON [a]

FromJSON (Ratio Integer)

FromJSON a => FromJSON (Maybe a)

HasResolution a => FromJSON (Fixed a)

WARNING: Only parse fixed-precision numbers from trusted input since an attacker could easily fill up the memory of the target system by specifying a scientific number with a big exponent like 1e1000000000.

FromJSON a => FromJSON (Dual a)

FromJSON a => FromJSON (First a)

FromJSON a => FromJSON (Last a)

FromJSON a => FromJSON (IntMap a)

(Ord a, FromJSON a) => FromJSON (Set a)

FromJSON v => FromJSON (Tree v)

(Eq a, Hashable a, FromJSON a) => FromJSON (HashSet a)

FromJSON a => FromJSON (Vector.Vector a)

(Vector Vector a, FromJSON a) => FromJSON (Vector a)

(Storable a, FromJSON a) => FromJSON (Vector a)

(Prim a, FromJSON a) => FromJSON (Vector a)

(FromJSON a, FromJSON b) => FromJSON (Either a b)

(FromJSON a, FromJSON b) => FromJSON (a, b)

FromJSON v => FromJSON (HashMap.HashMap String v)

FromJSON v => FromJSON (HashMap.HashMap Text.Text v)

FromJSON v => FromJSON (HashMap.HashMap Text v)

FromJSON v => FromJSON (Map String v)

FromJSON v => FromJSON (Map Text.Text v)

FromJSON v => FromJSON (Map Text v)

(FromJSON a, FromJSON b, FromJSON c) => FromJSON (a, b, c)

(FromJSON a, FromJSON b, FromJSON c, FromJSON d) => FromJSON (a, b, c, d)

(FromJSON a, FromJSON b, FromJSON c, FromJSON d, FromJSON e) => FromJSON (a, b, c, d, e)

(FromJSON a, FromJSON b, FromJSON c, FromJSON d, FromJSON e, FromJSON f) => FromJSON (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)

(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)

(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)

(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)

(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)

(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)

(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)

(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)

(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)

data Proxy t :: k -> *

A concrete, poly-kinded proxy type

Constructors

Proxy

Instances

Monad (Proxy *)

Functor (Proxy *)

Applicative (Proxy *)

Bounded (Proxy k s)

Enum (Proxy k s)

Eq (Proxy k s)

Data t => Data (Proxy * t)

Ord (Proxy k s)

Read (Proxy k s)

Show (Proxy k s)

Ix (Proxy k s)

Generic (Proxy * t)

Monoid (Proxy * s)

Generic (Proxy * t0)

HasDatatypeInfo (Proxy * t0)

Typeable (k -> *) (Proxy k)

type Rep (Proxy k t) = D1 D1Proxy (C1 C1_0Proxy U1)

type Code (Proxy * t0) = (:) [*] ([] *) ([] [*])