generic-aeson-0.2.0.7: Derivation of Aeson instances using GHC generics.

Safe HaskellNone
LanguageHaskell98

Generics.Generic.Aeson

Description

This module offers generic conversions to an from JSON Values for data types with a Generic instance.

The structure of the generated JSON is meant to be close to idiomatic JSON. This means:

  • Enumerations are converted to JSON strings.
  • Record fields become JSON keys.
  • Data types with one unlabeled field convert to just that field.
  • Data types with multiple unlabeled fields become arrays.
  • Multiple constructors are represented by keys.
  • Maybe values are either an absent key, or the value.

See 'tests/Main.hs' for more examples.

Synopsis

Documentation

gtoJson :: forall a. (Generic a, GtoJson (Rep a), ConNames (Rep a), GIsEnum (Rep a)) => a -> Value Source

Convert any datatype with a Generic instance to a JSON Value.

gparseJson :: forall a. (Generic a, GfromJson (Rep a), ConNames (Rep a), GIsEnum (Rep a)) => Value -> Parser a Source

Parse any datatype with a Generic instance from a JSON Value.

class GtoJson f where Source

Class for converting the functors from GHC.Generics to JSON. You generally don't need to give any custom instances. Just add 'deriving Generic' and call gToJson.

Methods

gtoJSONf :: Settings -> Bool -> Bool -> f a -> Either [Value] [(Text, Value)] Source

Generically show a functor as a JSON value. The first argument tells us if there are multiple constructors in the data type. The second indicates if this data type is an enumeration (only empty constructors). A functor is then converted to either a list of values (for non-labeled fields) or a list of String/value pairs (for labeled fields).

Instances

GtoJson U1 
ToJSON c => GtoJson (K1 a c) 
(GtoJson f, GtoJson g) => GtoJson ((:+:) f g) 
(GtoJson f, GtoJson g) => GtoJson ((:*:) f g) 
GtoJson f => GtoJson (M1 D c f) 
(Constructor c, GtoJson f) => GtoJson (M1 C c f) 
(Selector c, ToJSON a) => GtoJson (M1 S c (K1 i (Maybe a))) 
(Selector c, GtoJson f) => GtoJson (M1 S c f) 

class GfromJson f where Source

Class for parsing the functors from GHC.Generics from JSON. You generally don't need to give any custom instances. Just add 'deriving Generic' and call gFromJson.

Methods

gparseJSONf :: Settings -> Bool -> Bool -> Bool -> StateT [Value] Parser (f a) Source

Generically read a functor from a JSON value. The first argument tells us if there are multiple constructors in the data type. The second indicates if we've already detected that this data type has multiple constructors. When this is False, the (:*:) puts the fields in the state. The third indicates if this data type is an enumeration (only empty constructors). The third is a function for parsing the recursive positions. A JSON value is then parsed to either a functor, or a failure.

Instances

GfromJson U1 
FromJSON c => GfromJson (K1 a c) 
(GfromJson f, GfromJson g) => GfromJson ((:+:) f g) 
(GfromJson f, GfromJson g) => GfromJson ((:*:) f g) 
GfromJson f => GfromJson (M1 D c f) 
(Constructor c, GfromJson f) => GfromJson (M1 C c f) 
(Selector c, FromJSON a) => GfromJson (M1 S c (K1 i (Maybe a))) 
(Selector c, GfromJson f) => GfromJson (M1 S c f) 

formatLabel :: Settings -> Text -> Text Source

Lowercases the first letter and strips leading and trailing underscores.

data Settings Source

Constructors

Settings 

Instances

gtoJsonWithSettings :: forall a. (Generic a, GtoJson (Rep a), ConNames (Rep a), GIsEnum (Rep a)) => Settings -> a -> Value Source