aeson-1.4.2.0: Fast JSON parsing and encoding

Copyright(c) 2011-2016 Bryan O'Sullivan
(c) 2011 MailRank Inc.
LicenseBSD3
MaintainerBryan O'Sullivan <bos@serpentine.com>
Stabilityexperimental
Portabilityportable
Safe HaskellNone
LanguageHaskell2010

Data.Aeson

Contents

Description

Types and functions for working efficiently with JSON data.

(A note on naming: in Greek mythology, Aeson was the father of Jason.)

Synopsis

How to use this library

This section contains basic information on the different ways to work with data using this library. These range from simple but inflexible, to complex but flexible.

The most common way to use the library is to define a data type, corresponding to some JSON data you want to work with, and then write either a FromJSON instance, a to ToJSON instance, or both for that type.

For example, given this JSON data:

{ "name": "Joe", "age": 12 }

we create a matching data type:

{-# LANGUAGE DeriveGeneric #-}

import GHC.Generics

data Person = Person {
      name :: Text
    , age  :: Int
    } deriving (Generic, Show)

The LANGUAGE pragma and Generic instance let us write empty FromJSON and ToJSON instances for which the compiler will generate sensible default implementations.

instance ToJSON Person where
    -- No need to provide a toJSON implementation.

    -- For efficiency, we write a simple toEncoding implementation, as
    -- the default version uses toJSON.
    toEncoding = genericToEncoding defaultOptions

instance FromJSON Person
    -- No need to provide a parseJSON implementation.

We can now encode a value like so:

>>> encode (Person {name = "Joe", age = 12})
"{\"name\":\"Joe\",\"age\":12}"

Writing instances by hand

When necessary, we can write ToJSON and FromJSON instances by hand. This is valuable when the JSON-on-the-wire and Haskell data are different or otherwise need some more carefully managed translation. Let's revisit our JSON data:

{ "name": "Joe", "age": 12 }

We once again create a matching data type, without bothering to add a Generic instance this time:

data Person = Person {
      name :: Text
    , age  :: Int
    } deriving Show

To decode data, we need to define a FromJSON instance:

{-# LANGUAGE OverloadedStrings #-}

instance FromJSON Person where
    parseJSON = withObject "Person" $ \v -> Person
        <$> v .: "name"
        <*> v .: "age"

We can now parse the JSON data like so:

>>> decode "{\"name\":\"Joe\",\"age\":12}" :: Maybe Person
Just (Person {name = "Joe", age = 12})

To encode data, we need to define a ToJSON instance. Let's begin with an instance written entirely by hand.

instance ToJSON Person where
    -- this generates a Value
    toJSON (Person name age) =
        object ["name" .= name, "age" .= age]

    -- this encodes directly to a bytestring Builder
    toEncoding (Person name age) =
        pairs ("name" .= name <> "age" .= age)

We can now encode a value like so:

>>> encode (Person {name = "Joe", age = 12})
"{\"name\":\"Joe\",\"age\":12}"

There are predefined FromJSON and ToJSON instances for many types. Here's an example using lists and Ints:

>>> decode "[1,2,3]" :: Maybe [Int]
Just [1,2,3]

And here's an example using the Map type to get a map of Ints.

>>> decode "{\"foo\":1,\"bar\":2}" :: Maybe (Map String Int)
Just (fromList [("bar",2),("foo",1)])

Working with the AST

Sometimes you want to work with JSON data directly, without first converting it to a custom data type. This can be useful if you want to e.g. convert JSON data to YAML data, without knowing what the contents of the original JSON data was. The Value type, which is an instance of FromJSON, is used to represent an arbitrary JSON AST (abstract syntax tree). Example usage:

>>> decode "{\"foo\": 123}" :: Maybe Value
Just (Object (fromList [("foo",Number 123)]))
>>> decode "{\"foo\": [\"abc\",\"def\"]}" :: Maybe Value
Just (Object (fromList [("foo",Array (fromList [String "abc",String "def"]))]))

Once you have a Value you can write functions to traverse it and make arbitrary transformations.

Decoding to a Haskell value

We can decode to any instance of FromJSON:

λ> decode "[1,2,3]" :: Maybe [Int]
Just [1,2,3]

Alternatively, there are instances for standard data types, so you can use them directly. For example, use the Map type to get a map of Ints.

λ> import Data.Map
λ> decode "{\"foo\":1,\"bar\":2}" :: Maybe (Map String Int)
Just (fromList [("bar",2),("foo",1)])

Decoding a mixed-type object

The above approach with maps of course will not work for mixed-type objects that don't follow a strict schema, but there are a couple of approaches available for these.

The Object type contains JSON objects:

λ> decode "{\"name\":\"Dave\",\"age\":2}" :: Maybe Object
Just (fromList [("name",String "Dave"),("age",Number 2)])

You can extract values from it with a parser using parse, parseEither or, in this example, parseMaybe:

λ> do result <- decode "{\"name\":\"Dave\",\"age\":2}"
      flip parseMaybe result $ \obj -> do
        age <- obj .: "age"
        name <- obj .: "name"
        return (name ++ ": " ++ show (age*2))

Just "Dave: 4"

Considering that any type that implements FromJSON can be used here, this is quite a powerful way to parse JSON. See the documentation in FromJSON for how to implement this class for your own data types.

The downside is that you have to write the parser yourself; the upside is that you have complete control over the way the JSON is parsed.

Encoding and decoding

Decoding is a two-step process.

  • When decoding a value, the process is reversed: the bytes are converted to a Value, then the FromJSON class is used to convert to the desired type.

There are two ways to encode a value.

  • Convert to a Value using toJSON, then possibly further encode. This was the only method available in aeson 0.9 and earlier.
  • Directly encode (to what will become a ByteString) using toEncoding. This is much more efficient (about 3x faster, and less memory intensive besides), but is only available in aeson 0.10 and newer.

For convenience, the encode and decode functions combine both steps.

Direct encoding

In older versions of this library, encoding a Haskell value involved converting to an intermediate Value, then encoding that.

A "direct" encoder converts straight from a source Haskell value to a ByteString without constructing an intermediate Value. This approach is faster than toJSON, and allocates less memory. The toEncoding method makes it possible to implement direct encoding with low memory overhead.

To complicate matters, the default implementation of toEncoding uses toJSON. Why? The toEncoding method was added to this library much more recently than toJSON. Using toJSON ensures that packages written against older versions of this library will compile and produce correct output, but they will not see any speedup from direct encoding.

To write a minimal implementation of direct encoding, your type must implement GHC's Generic class, and your code should look like this:

    toEncoding = genericToEncoding defaultOptions

What if you have more elaborate encoding needs? For example, perhaps you need to change the names of object keys, omit parts of a value.

To encode to a JSON "object", use the pairs function.

    toEncoding (Person name age) =
        pairs ("name" .= name <> "age" .= age)

Any container type that implements Foldable can be encoded to a JSON "array" using foldable.

> import Data.Sequence as Seq
> encode (Seq.fromList [1,2,3])
"[1,2,3]"

decode :: FromJSON a => ByteString -> Maybe a #

Efficiently deserialize a JSON value from a lazy ByteString. If this fails due to incomplete or invalid input, Nothing is returned.

The input must consist solely of a JSON document, with no trailing data except for whitespace.

This function parses immediately, but defers conversion. See json for details.

decode' :: FromJSON a => ByteString -> Maybe a #

Efficiently deserialize a JSON value from a lazy ByteString. If this fails due to incomplete or invalid input, Nothing is returned.

The input must consist solely of a JSON document, with no trailing data except for whitespace.

This function parses and performs conversion immediately. See json' for details.

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

Like decode but returns an error message when decoding fails.

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.

encodeFile :: ToJSON a => FilePath -> a -> IO () #

Efficiently serialize a JSON value as a lazy ByteString and write it to a file.

Variants for strict bytestrings

decodeStrict :: FromJSON a => ByteString -> Maybe a #

Efficiently deserialize a JSON value from a strict ByteString. If this fails due to incomplete or invalid input, Nothing is returned.

The input must consist solely of a JSON document, with no trailing data except for whitespace.

This function parses immediately, but defers conversion. See json for details.

decodeFileStrict :: FromJSON a => FilePath -> IO (Maybe a) #

Efficiently deserialize a JSON value from a file. If this fails due to incomplete or invalid input, Nothing is returned.

The input file's content must consist solely of a JSON document, with no trailing data except for whitespace.

This function parses immediately, but defers conversion. See json for details.

decodeStrict' :: FromJSON a => ByteString -> Maybe a #

Efficiently deserialize a JSON value from a strict ByteString. If this fails due to incomplete or invalid input, Nothing is returned.

The input must consist solely of a JSON document, with no trailing data except for whitespace.

This function parses and performs conversion immediately. See json' for details.

decodeFileStrict' :: FromJSON a => FilePath -> IO (Maybe a) #

Efficiently deserialize a JSON value from a file. If this fails due to incomplete or invalid input, Nothing is returned.

The input file's content must consist solely of a JSON document, with no trailing data except for whitespace.

This function parses and performs conversion immediately. See json' for details.

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

Like decodeStrict but returns an error message when decoding fails.

eitherDecodeFileStrict :: FromJSON a => FilePath -> IO (Either String a) #

Like decodeFileStrict but returns an error message when decoding fails.

eitherDecodeStrict' :: FromJSON a => ByteString -> Either String a #

Like decodeStrict' but returns an error message when decoding fails.

eitherDecodeFileStrict' :: FromJSON a => FilePath -> IO (Either String a) #

Like decodeFileStrict' but returns an error message when decoding fails.

Core JSON types

data Value #

A JSON value represented as a Haskell value.

Instances
Eq Value # 
Instance details

Defined in Data.Aeson.Types.Internal

Methods

(==) :: Value -> Value -> Bool #

(/=) :: Value -> Value -> Bool #

Data Value # 
Instance details

Defined in Data.Aeson.Types.Internal

Methods

gfoldl :: (forall d b. Data d => c (d -> b) -> d -> c b) -> (forall g. g -> c g) -> Value -> c Value #

gunfold :: (forall b r. Data b => c (b -> r) -> c r) -> (forall r. r -> c r) -> Constr -> c Value #

toConstr :: Value -> Constr #

dataTypeOf :: Value -> DataType #

dataCast1 :: Typeable t => (forall d. Data d => c (t d)) -> Maybe (c Value) #

dataCast2 :: Typeable t => (forall d e. (Data d, Data e) => c (t d e)) -> Maybe (c Value) #

gmapT :: (forall b. Data b => b -> b) -> Value -> Value #

gmapQl :: (r -> r' -> r) -> r -> (forall d. Data d => d -> r') -> Value -> r #

gmapQr :: (r' -> r -> r) -> r -> (forall d. Data d => d -> r') -> Value -> r #

gmapQ :: (forall d. Data d => d -> u) -> Value -> [u] #

gmapQi :: Int -> (forall d. Data d => d -> u) -> Value -> u #

gmapM :: Monad m => (forall d. Data d => d -> m d) -> Value -> m Value #

gmapMp :: MonadPlus m => (forall d. Data d => d -> m d) -> Value -> m Value #

gmapMo :: MonadPlus m => (forall d. Data d => d -> m d) -> Value -> m Value #

Read Value # 
Instance details

Defined in Data.Aeson.Types.Internal

Show Value # 
Instance details

Defined in Data.Aeson.Types.Internal

Methods

showsPrec :: Int -> Value -> ShowS #

show :: Value -> String #

showList :: [Value] -> ShowS #

IsString Value # 
Instance details

Defined in Data.Aeson.Types.Internal

Methods

fromString :: String -> Value #

Generic Value # 
Instance details

Defined in Data.Aeson.Types.Internal

Associated Types

type Rep Value :: Type -> Type #

Methods

from :: Value -> Rep Value x #

to :: Rep Value x -> Value #

Lift Value # 
Instance details

Defined in Data.Aeson.Types.Internal

Methods

lift :: Value -> Q Exp #

NFData Value # 
Instance details

Defined in Data.Aeson.Types.Internal

Methods

rnf :: Value -> () #

Hashable Value # 
Instance details

Defined in Data.Aeson.Types.Internal

Methods

hashWithSalt :: Int -> Value -> Int #

hash :: Value -> Int #

FromJSON Value # 
Instance details

Defined in Data.Aeson.Types.FromJSON

KeyValue Pair # 
Instance details

Defined in Data.Aeson.Types.ToJSON

Methods

(.=) :: ToJSON v => Text -> v -> Pair #

KeyValue Object #

Constructs a singleton HashMap. For calling functions that demand an Object for constructing objects. To be used in conjunction with mconcat. Prefer to use object where possible.

Instance details

Defined in Data.Aeson.Types.ToJSON

Methods

(.=) :: ToJSON v => Text -> v -> Object #

ToJSON Value # 
Instance details

Defined in Data.Aeson.Types.ToJSON

type Rep Value # 
Instance details

Defined in Data.Aeson.Types.Internal

type Encoding = Encoding' Value #

Often used synonym for Encoding'.

fromEncoding :: Encoding' tag -> Builder #

Acquire the underlying bytestring builder.

type Array = Vector Value #

A JSON "array" (sequence).

type Object = HashMap Text Value #

A JSON "object" (key/value map).

Convenience types

newtype DotNetTime #

A newtype wrapper for UTCTime that uses the same non-standard serialization format as Microsoft .NET, whose System.DateTime type is by default serialized to JSON as in the following example:

/Date(1302547608878)/

The number represents milliseconds since the Unix epoch.

Constructors

DotNetTime 

Fields

Instances
Eq DotNetTime # 
Instance details

Defined in Data.Aeson.Types.Internal

Ord DotNetTime # 
Instance details

Defined in Data.Aeson.Types.Internal

Read DotNetTime # 
Instance details

Defined in Data.Aeson.Types.Internal

Show DotNetTime # 
Instance details

Defined in Data.Aeson.Types.Internal

FormatTime DotNetTime # 
Instance details

Defined in Data.Aeson.Types.Internal

FromJSON DotNetTime # 
Instance details

Defined in Data.Aeson.Types.FromJSON

ToJSON DotNetTime # 
Instance details

Defined in Data.Aeson.Types.ToJSON

Type conversion

class FromJSON a where #

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:

  • empty and mzero work, but are terse and uninformative;
  • fail yields a custom error message;
  • typeMismatch produces an informative message for cases when the value encountered is not of the expected type.

An example type and instance using typeMismatch:

-- 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 mzero to fail, but typeMismatch
    -- gives a much more informative error message.
    parseJSON invalid    = typeMismatch "Coord" invalid

For this common case of only being concerned with a single type of JSON value, the functions withObject, withNumber, 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

Minimal complete definition

Nothing

Instances
FromJSON Bool # 
Instance details

Defined in Data.Aeson.Types.FromJSON

FromJSON Char # 
Instance details

Defined in Data.Aeson.Types.FromJSON

FromJSON Double # 
Instance details

Defined in Data.Aeson.Types.FromJSON

FromJSON Float # 
Instance details

Defined in Data.Aeson.Types.FromJSON

FromJSON Int # 
Instance details

Defined in Data.Aeson.Types.FromJSON

FromJSON Int8 # 
Instance details

Defined in Data.Aeson.Types.FromJSON

FromJSON Int16 # 
Instance details

Defined in Data.Aeson.Types.FromJSON

FromJSON Int32 # 
Instance details

Defined in Data.Aeson.Types.FromJSON

FromJSON Int64 # 
Instance details

Defined in Data.Aeson.Types.FromJSON

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

FromJSON Natural # 
Instance details

Defined in Data.Aeson.Types.FromJSON

FromJSON Ordering # 
Instance details

Defined in Data.Aeson.Types.FromJSON

FromJSON Word # 
Instance details

Defined in Data.Aeson.Types.FromJSON

FromJSON Word8 # 
Instance details

Defined in Data.Aeson.Types.FromJSON

FromJSON Word16 # 
Instance details

Defined in Data.Aeson.Types.FromJSON

FromJSON Word32 # 
Instance details

Defined in Data.Aeson.Types.FromJSON

FromJSON Word64 # 
Instance details

Defined in Data.Aeson.Types.FromJSON

FromJSON () # 
Instance details

Defined in Data.Aeson.Types.FromJSON

Methods

parseJSON :: Value -> Parser () #

parseJSONList :: Value -> Parser [()] #

FromJSON Text # 
Instance details

Defined in Data.Aeson.Types.FromJSON

FromJSON Text # 
Instance details

Defined in Data.Aeson.Types.FromJSON

FromJSON Void # 
Instance details

Defined in Data.Aeson.Types.FromJSON

FromJSON Version # 
Instance details

Defined in Data.Aeson.Types.FromJSON

FromJSON CTime # 
Instance details

Defined in Data.Aeson.Types.FromJSON

FromJSON IntSet # 
Instance details

Defined in Data.Aeson.Types.FromJSON

FromJSON Scientific # 
Instance details

Defined in Data.Aeson.Types.FromJSON

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

FromJSON LocalTime # 
Instance details

Defined in Data.Aeson.Types.FromJSON

FromJSON TimeOfDay # 
Instance details

Defined in Data.Aeson.Types.FromJSON

FromJSON UTCTime # 
Instance details

Defined in Data.Aeson.Types.FromJSON

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

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

FromJSON Day # 
Instance details

Defined in Data.Aeson.Types.FromJSON

FromJSON UUID # 
Instance details

Defined in Data.Aeson.Types.FromJSON

FromJSON DotNetTime # 
Instance details

Defined in Data.Aeson.Types.FromJSON

FromJSON Value # 
Instance details

Defined in Data.Aeson.Types.FromJSON

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

(FromJSON a, Integral a) => FromJSON (Ratio a) # 
Instance details

Defined in Data.Aeson.Types.FromJSON

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

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

FromJSON a => FromJSON (Last a) # 
Instance details

Defined in Data.Aeson.Types.FromJSON

FromJSON a => FromJSON (WrappedMonoid a) # 
Instance details

Defined in Data.Aeson.Types.FromJSON

FromJSON a => FromJSON (Option a) # 
Instance details

Defined in Data.Aeson.Types.FromJSON

FromJSON a => FromJSON (Identity a) # 
Instance details

Defined in Data.Aeson.Types.FromJSON

FromJSON a => FromJSON (First a) # 
Instance details

Defined in Data.Aeson.Types.FromJSON

FromJSON a => FromJSON (Last a) # 
Instance details

Defined in Data.Aeson.Types.FromJSON

FromJSON a => FromJSON (Dual a) # 
Instance details

Defined in Data.Aeson.Types.FromJSON

FromJSON a => FromJSON (NonEmpty a) # 
Instance details

Defined in Data.Aeson.Types.FromJSON

FromJSON a => FromJSON (IntMap a) # 
Instance details

Defined in Data.Aeson.Types.FromJSON

FromJSON v => FromJSON (Tree v) # 
Instance details

Defined in Data.Aeson.Types.FromJSON

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] #

FromJSON a => FromJSON (DList a) # 
Instance details

Defined in Data.Aeson.Types.FromJSON

(PrimUnlifted a, FromJSON a) => FromJSON (UnliftedArray a) # 
Instance details

Defined in Data.Aeson.Types.FromJSON

(Prim a, FromJSON a) => FromJSON (PrimArray a) # 
Instance details

Defined in Data.Aeson.Types.FromJSON

FromJSON a => FromJSON (SmallArray a) # 
Instance details

Defined in Data.Aeson.Types.FromJSON

FromJSON a => FromJSON (Array a) # 
Instance details

Defined in Data.Aeson.Types.FromJSON

(Eq a, Hashable a, FromJSON a) => FromJSON (HashSet a) # 
Instance details

Defined in Data.Aeson.Types.FromJSON

(Vector Vector a, FromJSON a) => FromJSON (Vector a) # 
Instance details

Defined in Data.Aeson.Types.FromJSON

(Storable a, FromJSON a) => FromJSON (Vector a) # 
Instance details

Defined in Data.Aeson.Types.FromJSON

(Prim a, FromJSON a) => FromJSON (Vector a) # 
Instance details

Defined in Data.Aeson.Types.FromJSON

FromJSON a => FromJSON (Vector a) # 
Instance details

Defined in Data.Aeson.Types.FromJSON

(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 (Proxy a) # 
Instance details

Defined in Data.Aeson.Types.FromJSON

(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] #

(FromJSON v, FromJSONKey k, Eq k, Hashable k) => FromJSON (HashMap k v) # 
Instance details

Defined in Data.Aeson.Types.FromJSON

(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] #

(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 Result a #

The result of running a Parser.

Constructors

Error String 
Success a 
Instances
Monad Result # 
Instance details

Defined in Data.Aeson.Types.Internal

Methods

(>>=) :: Result a -> (a -> Result b) -> Result b #

(>>) :: Result a -> Result b -> Result b #

return :: a -> Result a #

fail :: String -> Result a #

Functor Result # 
Instance details

Defined in Data.Aeson.Types.Internal

Methods

fmap :: (a -> b) -> Result a -> Result b #

(<$) :: a -> Result b -> Result a #

MonadFail Result # 
Instance details

Defined in Data.Aeson.Types.Internal

Methods

fail :: String -> Result a #

Applicative Result # 
Instance details

Defined in Data.Aeson.Types.Internal

Methods

pure :: a -> Result a #

(<*>) :: Result (a -> b) -> Result a -> Result b #

liftA2 :: (a -> b -> c) -> Result a -> Result b -> Result c #

(*>) :: Result a -> Result b -> Result b #

(<*) :: Result a -> Result b -> Result a #

Foldable Result # 
Instance details

Defined in Data.Aeson.Types.Internal

Methods

fold :: Monoid m => Result m -> m #

foldMap :: Monoid m => (a -> m) -> Result a -> m #

foldr :: (a -> b -> b) -> b -> Result a -> b #

foldr' :: (a -> b -> b) -> b -> Result a -> b #

foldl :: (b -> a -> b) -> b -> Result a -> b #

foldl' :: (b -> a -> b) -> b -> Result a -> b #

foldr1 :: (a -> a -> a) -> Result a -> a #

foldl1 :: (a -> a -> a) -> Result a -> a #

toList :: Result a -> [a] #

null :: Result a -> Bool #

length :: Result a -> Int #

elem :: Eq a => a -> Result a -> Bool #

maximum :: Ord a => Result a -> a #

minimum :: Ord a => Result a -> a #

sum :: Num a => Result a -> a #

product :: Num a => Result a -> a #

Traversable Result # 
Instance details

Defined in Data.Aeson.Types.Internal

Methods

traverse :: Applicative f => (a -> f b) -> Result a -> f (Result b) #

sequenceA :: Applicative f => Result (f a) -> f (Result a) #

mapM :: Monad m => (a -> m b) -> Result a -> m (Result b) #

sequence :: Monad m => Result (m a) -> m (Result a) #

Alternative Result # 
Instance details

Defined in Data.Aeson.Types.Internal

Methods

empty :: Result a #

(<|>) :: Result a -> Result a -> Result a #

some :: Result a -> Result [a] #

many :: Result a -> Result [a] #

MonadPlus Result # 
Instance details

Defined in Data.Aeson.Types.Internal

Methods

mzero :: Result a #

mplus :: Result a -> Result a -> Result a #

Eq a => Eq (Result a) # 
Instance details

Defined in Data.Aeson.Types.Internal

Methods

(==) :: Result a -> Result a -> Bool #

(/=) :: Result a -> Result a -> Bool #

Show a => Show (Result a) # 
Instance details

Defined in Data.Aeson.Types.Internal

Methods

showsPrec :: Int -> Result a -> ShowS #

show :: Result a -> String #

showList :: [Result a] -> ShowS #

Semigroup (Result a) # 
Instance details

Defined in Data.Aeson.Types.Internal

Methods

(<>) :: Result a -> Result a -> Result a #

sconcat :: NonEmpty (Result a) -> Result a #

stimes :: Integral b => b -> Result a -> Result a #

Monoid (Result a) # 
Instance details

Defined in Data.Aeson.Types.Internal

Methods

mempty :: Result a #

mappend :: Result a -> Result a -> Result a #

mconcat :: [Result a] -> Result a #

NFData a => NFData (Result a) # 
Instance details

Defined in Data.Aeson.Types.Internal

Methods

rnf :: Result a -> () #

fromJSON :: FromJSON a => Value -> Result a #

Convert a value from JSON, failing if the types do not match.

class ToJSON a where #

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:

  1. 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.
  2. 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.)

Minimal complete definition

Nothing

Methods

toJSON :: a -> Value #

Convert a Haskell value to a JSON-friendly intermediate type.

toJSON :: (Generic a, GToJSON Value Zero (Rep a)) => a -> Value #

Convert a Haskell value to a JSON-friendly intermediate type.

toEncoding :: a -> Encoding #

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.

instance ToJSON Coord where
    toEncoding = genericToEncoding defaultOptions

toJSONList :: [a] -> Value #

toEncodingList :: [a] -> Encoding #

Instances
ToJSON Bool # 
Instance details

Defined in Data.Aeson.Types.ToJSON

ToJSON Char # 
Instance details

Defined in Data.Aeson.Types.ToJSON

ToJSON Double # 
Instance details

Defined in Data.Aeson.Types.ToJSON

ToJSON Float # 
Instance details

Defined in Data.Aeson.Types.ToJSON

ToJSON Int # 
Instance details

Defined in Data.Aeson.Types.ToJSON

ToJSON Int8 # 
Instance details

Defined in Data.Aeson.Types.ToJSON

ToJSON Int16 # 
Instance details

Defined in Data.Aeson.Types.ToJSON

ToJSON Int32 # 
Instance details

Defined in Data.Aeson.Types.ToJSON

ToJSON Int64 # 
Instance details

Defined in Data.Aeson.Types.ToJSON

ToJSON Integer # 
Instance details

Defined in Data.Aeson.Types.ToJSON

ToJSON Natural # 
Instance details

Defined in Data.Aeson.Types.ToJSON

ToJSON Ordering # 
Instance details

Defined in Data.Aeson.Types.ToJSON

ToJSON Word # 
Instance details

Defined in Data.Aeson.Types.ToJSON

ToJSON Word8 # 
Instance details

Defined in Data.Aeson.Types.ToJSON

ToJSON Word16 # 
Instance details

Defined in Data.Aeson.Types.ToJSON

ToJSON Word32 # 
Instance details

Defined in Data.Aeson.Types.ToJSON

ToJSON Word64 # 
Instance details

Defined in Data.Aeson.Types.ToJSON

ToJSON () # 
Instance details

Defined in Data.Aeson.Types.ToJSON

Methods

toJSON :: () -> Value #

toEncoding :: () -> Encoding #

toJSONList :: [()] -> Value #

toEncodingList :: [()] -> Encoding #

ToJSON Text # 
Instance details

Defined in Data.Aeson.Types.ToJSON

ToJSON Text # 
Instance details

Defined in Data.Aeson.Types.ToJSON

ToJSON Number # 
Instance details

Defined in Data.Aeson.Types.ToJSON

ToJSON Void # 
Instance details

Defined in Data.Aeson.Types.ToJSON

ToJSON Version # 
Instance details

Defined in Data.Aeson.Types.ToJSON

ToJSON CTime # 
Instance details

Defined in Data.Aeson.Types.ToJSON

ToJSON IntSet # 
Instance details

Defined in Data.Aeson.Types.ToJSON

ToJSON Scientific # 
Instance details

Defined in Data.Aeson.Types.ToJSON

ToJSON ZonedTime # 
Instance details

Defined in Data.Aeson.Types.ToJSON

ToJSON LocalTime # 
Instance details

Defined in Data.Aeson.Types.ToJSON

ToJSON TimeOfDay # 
Instance details

Defined in Data.Aeson.Types.ToJSON

ToJSON UTCTime # 
Instance details

Defined in Data.Aeson.Types.ToJSON

ToJSON NominalDiffTime # 
Instance details

Defined in Data.Aeson.Types.ToJSON

ToJSON DiffTime # 
Instance details

Defined in Data.Aeson.Types.ToJSON

ToJSON Day # 
Instance details

Defined in Data.Aeson.Types.ToJSON

ToJSON UUID # 
Instance details

Defined in Data.Aeson.Types.ToJSON

ToJSON DotNetTime # 
Instance details

Defined in Data.Aeson.Types.ToJSON

ToJSON Value # 
Instance details

Defined in Data.Aeson.Types.ToJSON

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

(ToJSON a, Integral a) => ToJSON (Ratio a) # 
Instance details

Defined in Data.Aeson.Types.ToJSON

HasResolution a => ToJSON (Fixed a) # 
Instance details

Defined in Data.Aeson.Types.ToJSON

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

ToJSON a => ToJSON (Last a) # 
Instance details

Defined in Data.Aeson.Types.ToJSON

ToJSON a => ToJSON (WrappedMonoid a) # 
Instance details

Defined in Data.Aeson.Types.ToJSON

ToJSON a => ToJSON (Option a) # 
Instance details

Defined in Data.Aeson.Types.ToJSON

ToJSON a => ToJSON (Identity a) # 
Instance details

Defined in Data.Aeson.Types.ToJSON

ToJSON a => ToJSON (First a) # 
Instance details

Defined in Data.Aeson.Types.ToJSON

ToJSON a => ToJSON (Last a) # 
Instance details

Defined in Data.Aeson.Types.ToJSON

ToJSON a => ToJSON (Dual a) # 
Instance details

Defined in Data.Aeson.Types.ToJSON

ToJSON a => ToJSON (NonEmpty a) # 
Instance details

Defined in Data.Aeson.Types.ToJSON

ToJSON a => ToJSON (IntMap a) # 
Instance details

Defined in Data.Aeson.Types.ToJSON

ToJSON v => ToJSON (Tree v) # 
Instance details

Defined in Data.Aeson.Types.ToJSON

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 #

ToJSON a => ToJSON (DList a) # 
Instance details

Defined in Data.Aeson.Types.ToJSON

(PrimUnlifted a, ToJSON a) => ToJSON (UnliftedArray a) # 
Instance details

Defined in Data.Aeson.Types.ToJSON

(Prim a, ToJSON a) => ToJSON (PrimArray a) # 
Instance details

Defined in Data.Aeson.Types.ToJSON

ToJSON a => ToJSON (SmallArray a) # 
Instance details

Defined in Data.Aeson.Types.ToJSON

ToJSON a => ToJSON (Array a) # 
Instance details

Defined in Data.Aeson.Types.ToJSON

ToJSON a => ToJSON (HashSet a) # 
Instance details

Defined in Data.Aeson.Types.ToJSON

(Vector Vector a, ToJSON a) => ToJSON (Vector a) # 
Instance details

Defined in Data.Aeson.Types.ToJSON

(Storable a, ToJSON a) => ToJSON (Vector a) # 
Instance details

Defined in Data.Aeson.Types.ToJSON

(Prim a, ToJSON a) => ToJSON (Vector a) # 
Instance details

Defined in Data.Aeson.Types.ToJSON

ToJSON a => ToJSON (Vector a) # 
Instance details

Defined in Data.Aeson.Types.ToJSON

(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 (Proxy a) # 
Instance details

Defined in Data.Aeson.Types.ToJSON

(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 #

(ToJSON v, ToJSONKey k) => ToJSON (HashMap k v) # 
Instance details

Defined in Data.Aeson.Types.ToJSON

(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 #

(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 #

class KeyValue kv where #

A key-value pair for encoding a JSON object.

Methods

(.=) :: ToJSON v => Text -> v -> kv infixr 8 #

Instances
KeyValue Pair # 
Instance details

Defined in Data.Aeson.Types.ToJSON

Methods

(.=) :: ToJSON v => Text -> v -> Pair #

KeyValue Object #

Constructs a singleton HashMap. For calling functions that demand an Object for constructing objects. To be used in conjunction with mconcat. Prefer to use object where possible.

Instance details

Defined in Data.Aeson.Types.ToJSON

Methods

(.=) :: ToJSON v => Text -> v -> Object #

KeyValue Series # 
Instance details

Defined in Data.Aeson.Types.ToJSON

Methods

(.=) :: ToJSON v => Text -> v -> Series #

Keys for maps

class ToJSONKey a where #

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 Foo

That'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, in this example, ToJSONKeyText will be used instead of ToJSONKeyValue. 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.Encoding

The 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 Value 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.Encoding

This 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 #

Strategy for rendering the key for a map-like container.

toJSONKey :: ToJSON a => ToJSONKeyFunction a #

Strategy for rendering the key for a map-like container.

toJSONKeyList :: ToJSONKeyFunction [a] #

This is similar in spirit to the showsList method of Show. It makes it possible to give Value keys special treatment without using OverlappingInstances. End users should always be able to use the default implementation of this method.

toJSONKeyList :: ToJSON a => ToJSONKeyFunction [a] #

This is similar in spirit to the showsList method of Show. It makes it possible to give Value keys special treatment without using OverlappingInstances. End users should always be able to use the default implementation of this method.

Instances
ToJSONKey Bool # 
Instance details

Defined in Data.Aeson.Types.ToJSON

ToJSONKey Char # 
Instance details

Defined in Data.Aeson.Types.ToJSON

ToJSONKey Double # 
Instance details

Defined in Data.Aeson.Types.ToJSON

ToJSONKey Float # 
Instance details

Defined in Data.Aeson.Types.ToJSON

ToJSONKey Int # 
Instance details

Defined in Data.Aeson.Types.ToJSON

ToJSONKey Int8 # 
Instance details

Defined in Data.Aeson.Types.ToJSON

ToJSONKey Int16 # 
Instance details

Defined in Data.Aeson.Types.ToJSON

ToJSONKey Int32 # 
Instance details

Defined in Data.Aeson.Types.ToJSON

ToJSONKey Int64 # 
Instance details

Defined in Data.Aeson.Types.ToJSON

ToJSONKey Integer # 
Instance details

Defined in Data.Aeson.Types.ToJSON

ToJSONKey Natural # 
Instance details

Defined in Data.Aeson.Types.ToJSON

ToJSONKey Word # 
Instance details

Defined in Data.Aeson.Types.ToJSON

ToJSONKey Word8 # 
Instance details

Defined in Data.Aeson.Types.ToJSON

ToJSONKey Word16 # 
Instance details

Defined in Data.Aeson.Types.ToJSON

ToJSONKey Word32 # 
Instance details

Defined in Data.Aeson.Types.ToJSON

ToJSONKey Word64 # 
Instance details

Defined in Data.Aeson.Types.ToJSON

ToJSONKey Text # 
Instance details

Defined in Data.Aeson.Types.ToJSON

ToJSONKey Text # 
Instance details

Defined in Data.Aeson.Types.ToJSON

ToJSONKey Version # 
Instance details

Defined in Data.Aeson.Types.ToJSON

ToJSONKey Scientific # 
Instance details

Defined in Data.Aeson.Types.ToJSON

ToJSONKey ZonedTime # 
Instance details

Defined in Data.Aeson.Types.ToJSON

ToJSONKey LocalTime # 
Instance details

Defined in Data.Aeson.Types.ToJSON

ToJSONKey TimeOfDay # 
Instance details

Defined in Data.Aeson.Types.ToJSON

ToJSONKey UTCTime # 
Instance details

Defined in Data.Aeson.Types.ToJSON

ToJSONKey Day # 
Instance details

Defined in Data.Aeson.Types.ToJSON

ToJSONKey UUID # 
Instance details

Defined in Data.Aeson.Types.ToJSON

(ToJSONKey a, ToJSON a) => ToJSONKey [a] # 
Instance details

Defined in Data.Aeson.Types.ToJSON

HasResolution a => ToJSONKey (Fixed a) # 
Instance details

Defined in Data.Aeson.Types.ToJSON

ToJSONKey a => ToJSONKey (Identity a) # 
Instance details

Defined in Data.Aeson.Types.ToJSON

(ToJSON a, ToJSON b) => ToJSONKey (a, b) # 
Instance details

Defined in Data.Aeson.Types.ToJSON

(ToJSON a, ToJSON b, ToJSON c) => ToJSONKey (a, b, c) # 
Instance details

Defined in Data.Aeson.Types.ToJSON

Methods

toJSONKey :: ToJSONKeyFunction (a, b, c) #

toJSONKeyList :: ToJSONKeyFunction [(a, b, c)] #

ToJSONKey b => ToJSONKey (Tagged a b) # 
Instance details

Defined in Data.Aeson.Types.ToJSON

(ToJSON a, ToJSON b, ToJSON c, ToJSON d) => ToJSONKey (a, b, c, d) # 
Instance details

Defined in Data.Aeson.Types.ToJSON

Methods

toJSONKey :: ToJSONKeyFunction (a, b, c, d) #

toJSONKeyList :: ToJSONKeyFunction [(a, b, c, d)] #

data ToJSONKeyFunction a #

Constructors

ToJSONKeyText !(a -> Text) !(a -> Encoding' Text)

key is encoded to string, produces object

ToJSONKeyValue !(a -> Value) !(a -> Encoding)

key is encoded to value, produces array

Instances
Contravariant ToJSONKeyFunction # 
Instance details

Defined in Data.Aeson.Types.ToJSON

class FromJSONKey a where #

Read the docs for ToJSONKey first. This class is a conversion in the opposite direction. If you have a newtype wrapper around Text, the recommended way to define instances is with generalized newtype deriving:

newtype SomeId = SomeId { getSomeId :: Text }
  deriving (Eq,Ord,Hashable,FromJSONKey)

Minimal complete definition

Nothing

Methods

fromJSONKey :: FromJSONKeyFunction a #

Strategy for parsing the key of a map-like container.

fromJSONKey :: FromJSON a => FromJSONKeyFunction a #

Strategy for parsing the key of a map-like container.

fromJSONKeyList :: FromJSONKeyFunction [a] #

This is similar in spirit to the readList method of Read. It makes it possible to give Value keys special treatment without using OverlappingInstances. End users should always be able to use the default implementation of this method.

fromJSONKeyList :: FromJSON a => FromJSONKeyFunction [a] #

This is similar in spirit to the readList method of Read. It makes it possible to give Value keys special treatment without using OverlappingInstances. End users should always be able to use the default implementation of this method.

Instances
FromJSONKey Bool # 
Instance details

Defined in Data.Aeson.Types.FromJSON

FromJSONKey Char # 
Instance details

Defined in Data.Aeson.Types.FromJSON

FromJSONKey Double # 
Instance details

Defined in Data.Aeson.Types.FromJSON

FromJSONKey Float # 
Instance details

Defined in Data.Aeson.Types.FromJSON

FromJSONKey Int # 
Instance details

Defined in Data.Aeson.Types.FromJSON

FromJSONKey Int8 # 
Instance details

Defined in Data.Aeson.Types.FromJSON

FromJSONKey Int16 # 
Instance details

Defined in Data.Aeson.Types.FromJSON

FromJSONKey Int32 # 
Instance details

Defined in Data.Aeson.Types.FromJSON

FromJSONKey Int64 # 
Instance details

Defined in Data.Aeson.Types.FromJSON

FromJSONKey Integer # 
Instance details

Defined in Data.Aeson.Types.FromJSON

FromJSONKey Natural # 
Instance details

Defined in Data.Aeson.Types.FromJSON

FromJSONKey Word # 
Instance details

Defined in Data.Aeson.Types.FromJSON

FromJSONKey Word8 # 
Instance details

Defined in Data.Aeson.Types.FromJSON

FromJSONKey Word16 # 
Instance details

Defined in Data.Aeson.Types.FromJSON

FromJSONKey Word32 # 
Instance details

Defined in Data.Aeson.Types.FromJSON

FromJSONKey Word64 # 
Instance details

Defined in Data.Aeson.Types.FromJSON

FromJSONKey Text # 
Instance details

Defined in Data.Aeson.Types.FromJSON

FromJSONKey Text # 
Instance details

Defined in Data.Aeson.Types.FromJSON

FromJSONKey Version # 
Instance details

Defined in Data.Aeson.Types.FromJSON

FromJSONKey ZonedTime # 
Instance details

Defined in Data.Aeson.Types.FromJSON

FromJSONKey LocalTime # 
Instance details

Defined in Data.Aeson.Types.FromJSON

FromJSONKey TimeOfDay # 
Instance details

Defined in Data.Aeson.Types.FromJSON

FromJSONKey UTCTime # 
Instance details

Defined in Data.Aeson.Types.FromJSON

FromJSONKey Day # 
Instance details

Defined in Data.Aeson.Types.FromJSON

FromJSONKey UUID # 
Instance details

Defined in Data.Aeson.Types.FromJSON

(FromJSONKey a, FromJSON a) => FromJSONKey [a] # 
Instance details

Defined in Data.Aeson.Types.FromJSON

FromJSONKey a => FromJSONKey (Identity a) # 
Instance details

Defined in Data.Aeson.Types.FromJSON

(FromJSON a, FromJSON b) => FromJSONKey (a, b) # 
Instance details

Defined in Data.Aeson.Types.FromJSON

(FromJSON a, FromJSON b, FromJSON c) => FromJSONKey (a, b, c) # 
Instance details

Defined in Data.Aeson.Types.FromJSON

FromJSONKey b => FromJSONKey (Tagged a b) # 
Instance details

Defined in Data.Aeson.Types.FromJSON

(FromJSON a, FromJSON b, FromJSON c, FromJSON d) => FromJSONKey (a, b, c, d) # 
Instance details

Defined in Data.Aeson.Types.FromJSON

Methods

fromJSONKey :: FromJSONKeyFunction (a, b, c, d) #

fromJSONKeyList :: FromJSONKeyFunction [(a, b, c, d)] #

data FromJSONKeyFunction a #

This type is related to ToJSONKeyFunction. If FromJSONKeyValue is used in the FromJSONKey instance, then ToJSONKeyValue should be used in the ToJSONKey instance. The other three data constructors for this type all correspond to ToJSONKeyText. Strictly speaking, FromJSONKeyTextParser is more powerful than FromJSONKeyText, which is in turn more powerful than FromJSONKeyCoerce. For performance reasons, these exist as three options instead of one.

Constructors

FromJSONKeyCoerce !(CoerceText a)

uses coerce (unsafeCoerce in older GHCs)

FromJSONKeyText !(Text -> a)

conversion from Text that always succeeds

FromJSONKeyTextParser !(Text -> Parser a)

conversion from Text that may fail

FromJSONKeyValue !(Value -> Parser a)

conversion for non-textual keys

Instances
Functor FromJSONKeyFunction #

Only law abiding up to interpretation

Instance details

Defined in Data.Aeson.Types.FromJSON

Liftings to unary and binary type constructors

class FromJSON1 f where #

Lifting of the FromJSON class to unary type constructors.

Instead of manually writing your FromJSON1 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 liftParseJSON.

To use the second, simply add a deriving Generic1 clause to your datatype and declare a FromJSON1 instance for your datatype without giving a definition for liftParseJSON.

For example:

{-# LANGUAGE DeriveGeneric #-}

import GHC.Generics

data Pair a b = Pair { pairFst :: a, pairSnd :: b } deriving Generic1

instance FromJSON a => FromJSON1 (Pair a)

If the default implementation doesn't give exactly the results you want, you can customize the generic decoding with only a tiny amount of effort, using genericLiftParseJSON with your preferred Options:

customOptions = defaultOptions
                { fieldLabelModifier = map toUpper
                }

instance FromJSON a => FromJSON1 (Pair a) where
    liftParseJSON = genericLiftParseJSON customOptions

Minimal complete definition

Nothing

Methods

liftParseJSON :: (Value -> Parser a) -> (Value -> Parser [a]) -> Value -> Parser (f a) #

liftParseJSON :: (Generic1 f, GFromJSON One (Rep1 f)) => (Value -> Parser a) -> (Value -> Parser [a]) -> Value -> Parser (f a) #

liftParseJSONList :: (Value -> Parser a) -> (Value -> Parser [a]) -> Value -> Parser [f a] #

Instances
FromJSON1 [] # 
Instance details

Defined in Data.Aeson.Types.FromJSON

Methods

liftParseJSON :: (Value -> Parser a) -> (Value -> Parser [a]) -> Value -> Parser [a] #

liftParseJSONList :: (Value -> Parser a) -> (Value -> Parser [a]) -> Value -> Parser [[a]] #

FromJSON1 Maybe # 
Instance details

Defined in Data.Aeson.Types.FromJSON

Methods

liftParseJSON :: (Value -> Parser a) -> (Value -> Parser [a]) -> Value -> Parser (Maybe a) #

liftParseJSONList :: (Value -> Parser a) -> (Value -> Parser [a]) -> Value -> Parser [Maybe a] #

FromJSON1 Min # 
Instance details

Defined in Data.Aeson.Types.FromJSON

Methods

liftParseJSON :: (Value -> Parser a) -> (Value -> Parser [a]) -> Value -> Parser (Min a) #

liftParseJSONList :: (Value -> Parser a) -> (Value -> Parser [a]) -> Value -> Parser [Min a] #

FromJSON1 Max # 
Instance details

Defined in Data.Aeson.Types.FromJSON

Methods

liftParseJSON :: (Value -> Parser a) -> (Value -> Parser [a]) -> Value -> Parser (Max a) #

liftParseJSONList :: (Value -> Parser a) -> (Value -> Parser [a]) -> Value -> Parser [Max a] #

FromJSON1 First # 
Instance details

Defined in Data.Aeson.Types.FromJSON

Methods

liftParseJSON :: (Value -> Parser a) -> (Value -> Parser [a]) -> Value -> Parser (First a) #

liftParseJSONList :: (Value -> Parser a) -> (Value -> Parser [a]) -> Value -> Parser [First a] #

FromJSON1 Last # 
Instance details

Defined in Data.Aeson.Types.FromJSON

Methods

liftParseJSON :: (Value -> Parser a) -> (Value -> Parser [a]) -> Value -> Parser (Last a) #

liftParseJSONList :: (Value -> Parser a) -> (Value -> Parser [a]) -> Value -> Parser [Last a] #

FromJSON1 WrappedMonoid # 
Instance details

Defined in Data.Aeson.Types.FromJSON

Methods

liftParseJSON :: (Value -> Parser a) -> (Value -> Parser [a]) -> Value -> Parser (WrappedMonoid a) #

liftParseJSONList :: (Value -> Parser a) -> (Value -> Parser [a]) -> Value -> Parser [WrappedMonoid a] #

FromJSON1 Option # 
Instance details

Defined in Data.Aeson.Types.FromJSON

Methods

liftParseJSON :: (Value -> Parser a) -> (Value -> Parser [a]) -> Value -> Parser (Option a) #

liftParseJSONList :: (Value -> Parser a) -> (Value -> Parser [a]) -> Value -> Parser [Option a] #

FromJSON1 Identity # 
Instance details

Defined in Data.Aeson.Types.FromJSON

Methods

liftParseJSON :: (Value -> Parser a) -> (Value -> Parser [a]) -> Value -> Parser (Identity a) #

liftParseJSONList :: (Value -> Parser a) -> (Value -> Parser [a]) -> Value -> Parser [Identity a] #

FromJSON1 First # 
Instance details

Defined in Data.Aeson.Types.FromJSON

Methods

liftParseJSON :: (Value -> Parser a) -> (Value -> Parser [a]) -> Value -> Parser (First a) #

liftParseJSONList :: (Value -> Parser a) -> (Value -> Parser [a]) -> Value -> Parser [First a] #

FromJSON1 Last # 
Instance details

Defined in Data.Aeson.Types.FromJSON

Methods

liftParseJSON :: (Value -> Parser a) -> (Value -> Parser [a]) -> Value -> Parser (Last a) #

liftParseJSONList :: (Value -> Parser a) -> (Value -> Parser [a]) -> Value -> Parser [Last a] #

FromJSON1 Dual # 
Instance details

Defined in Data.Aeson.Types.FromJSON

Methods

liftParseJSON :: (Value -> Parser a) -> (Value -> Parser [a]) -> Value -> Parser (Dual a) #

liftParseJSONList :: (Value -> Parser a) -> (Value -> Parser [a]) -> Value -> Parser [Dual a] #

FromJSON1 NonEmpty # 
Instance details

Defined in Data.Aeson.Types.FromJSON

Methods

liftParseJSON :: (Value -> Parser a) -> (Value -> Parser [a]) -> Value -> Parser (NonEmpty a) #

liftParseJSONList :: (Value -> Parser a) -> (Value -> Parser [a]) -> Value -> Parser [NonEmpty a] #

FromJSON1 IntMap # 
Instance details

Defined in Data.Aeson.Types.FromJSON

Methods

liftParseJSON :: (Value -> Parser a) -> (Value -> Parser [a]) -> Value -> Parser (IntMap a) #

liftParseJSONList :: (Value -> Parser a) -> (Value -> Parser [a]) -> Value -> Parser [IntMap a] #

FromJSON1 Tree # 
Instance details

Defined in Data.Aeson.Types.FromJSON

Methods

liftParseJSON :: (Value -> Parser a) -> (Value -> Parser [a]) -> Value -> Parser (Tree a) #

liftParseJSONList :: (Value -> Parser a) -> (Value -> Parser [a]) -> Value -> Parser [Tree a] #

FromJSON1 Seq # 
Instance details

Defined in Data.Aeson.Types.FromJSON

Methods

liftParseJSON :: (Value -> Parser a) -> (Value -> Parser [a]) -> Value -> Parser (Seq a) #

liftParseJSONList :: (Value -> Parser a) -> (Value -> Parser [a]) -> Value -> Parser [Seq a] #

FromJSON1 DList # 
Instance details

Defined in Data.Aeson.Types.FromJSON

Methods

liftParseJSON :: (Value -> Parser a) -> (Value -> Parser [a]) -> Value -> Parser (DList a) #

liftParseJSONList :: (Value -> Parser a) -> (Value -> Parser [a]) -> Value -> Parser [DList a] #

FromJSON1 Vector # 
Instance details

Defined in Data.Aeson.Types.FromJSON

Methods

liftParseJSON :: (Value -> Parser a) -> (Value -> Parser [a]) -> Value -> Parser (Vector a) #

liftParseJSONList :: (Value -> Parser a) -> (Value -> Parser [a]) -> Value -> Parser [Vector a] #

FromJSON a => FromJSON1 (Either a) # 
Instance details

Defined in Data.Aeson.Types.FromJSON

Methods

liftParseJSON :: (Value -> Parser a0) -> (Value -> Parser [a0]) -> Value -> Parser (Either a a0) #

liftParseJSONList :: (Value -> Parser a0) -> (Value -> Parser [a0]) -> Value -> Parser [Either a a0] #

FromJSON a => FromJSON1 ((,) a) # 
Instance details

Defined in Data.Aeson.Types.FromJSON

Methods

liftParseJSON :: (Value -> Parser a0) -> (Value -> Parser [a0]) -> Value -> Parser (a, a0) #

liftParseJSONList :: (Value -> Parser a0) -> (Value -> Parser [a0]) -> Value -> Parser [(a, a0)] #

FromJSON1 (Proxy :: Type -> Type) # 
Instance details

Defined in Data.Aeson.Types.FromJSON

Methods

liftParseJSON :: (Value -> Parser a) -> (Value -> Parser [a]) -> Value -> Parser (Proxy a) #

liftParseJSONList :: (Value -> Parser a) -> (Value -> Parser [a]) -> Value -> Parser [Proxy a] #

(FromJSONKey k, Ord k) => FromJSON1 (Map k) # 
Instance details

Defined in Data.Aeson.Types.FromJSON

Methods

liftParseJSON :: (Value -> Parser a) -> (Value -> Parser [a]) -> Value -> Parser (Map k a) #

liftParseJSONList :: (Value -> Parser a) -> (Value -> Parser [a]) -> Value -> Parser [Map k a] #

(FromJSONKey k, Eq k, Hashable k) => FromJSON1 (HashMap k) # 
Instance details

Defined in Data.Aeson.Types.FromJSON

Methods

liftParseJSON :: (Value -> Parser a) -> (Value -> Parser [a]) -> Value -> Parser (HashMap k a) #

liftParseJSONList :: (Value -> Parser a) -> (Value -> Parser [a]) -> Value -> Parser [HashMap k a] #

(FromJSON a, FromJSON b) => FromJSON1 ((,,) a b) # 
Instance details

Defined in Data.Aeson.Types.FromJSON

Methods

liftParseJSON :: (Value -> Parser a0) -> (Value -> Parser [a0]) -> Value -> Parser (a, b, a0) #

liftParseJSONList :: (Value -> Parser a0) -> (Value -> Parser [a0]) -> Value -> Parser [(a, b, a0)] #

FromJSON a => FromJSON1 (Const a :: Type -> Type) # 
Instance details

Defined in Data.Aeson.Types.FromJSON

Methods

liftParseJSON :: (Value -> Parser a0) -> (Value -> Parser [a0]) -> Value -> Parser (Const a a0) #

liftParseJSONList :: (Value -> Parser a0) -> (Value -> Parser [a0]) -> Value -> Parser [Const a a0] #

FromJSON1 (Tagged a) # 
Instance details

Defined in Data.Aeson.Types.FromJSON

Methods

liftParseJSON :: (Value -> Parser a0) -> (Value -> Parser [a0]) -> Value -> Parser (Tagged a a0) #

liftParseJSONList :: (Value -> Parser a0) -> (Value -> Parser [a0]) -> Value -> Parser [Tagged a a0] #

(FromJSON a, FromJSON b, FromJSON c) => FromJSON1 ((,,,) a b c) # 
Instance details

Defined in Data.Aeson.Types.FromJSON

Methods

liftParseJSON :: (Value -> Parser a0) -> (Value -> Parser [a0]) -> Value -> Parser (a, b, c, a0) #

liftParseJSONList :: (Value -> Parser a0) -> (Value -> Parser [a0]) -> Value -> Parser [(a, b, c, a0)] #

(FromJSON1 f, FromJSON1 g) => FromJSON1 (Product f g) # 
Instance details

Defined in Data.Aeson.Types.FromJSON

Methods

liftParseJSON :: (Value -> Parser a) -> (Value -> Parser [a]) -> Value -> Parser (Product f g a) #

liftParseJSONList :: (Value -> Parser a) -> (Value -> Parser [a]) -> Value -> Parser [Product f g a] #

(FromJSON1 f, FromJSON1 g) => FromJSON1 (Sum f g) # 
Instance details

Defined in Data.Aeson.Types.FromJSON

Methods

liftParseJSON :: (Value -> Parser a) -> (Value -> Parser [a]) -> Value -> Parser (Sum f g a) #

liftParseJSONList :: (Value -> Parser a) -> (Value -> Parser [a]) -> Value -> Parser [Sum f g a] #

(FromJSON a, FromJSON b, FromJSON c, FromJSON d) => FromJSON1 ((,,,,) a b c d) # 
Instance details

Defined in Data.Aeson.Types.FromJSON

Methods

liftParseJSON :: (Value -> Parser a0) -> (Value -> Parser [a0]) -> Value -> Parser (a, b, c, d, a0) #

liftParseJSONList :: (Value -> Parser a0) -> (Value -> Parser [a0]) -> Value -> Parser [(a, b, c, d, a0)] #

(FromJSON1 f, FromJSON1 g) => FromJSON1 (Compose f g) # 
Instance details

Defined in Data.Aeson.Types.FromJSON

Methods

liftParseJSON :: (Value -> Parser a) -> (Value -> Parser [a]) -> Value -> Parser (Compose f g a) #

liftParseJSONList :: (Value -> Parser a) -> (Value -> Parser [a]) -> Value -> Parser [Compose f g a] #

(FromJSON a, FromJSON b, FromJSON c, FromJSON d, FromJSON e) => FromJSON1 ((,,,,,) a b c d e) # 
Instance details

Defined in Data.Aeson.Types.FromJSON

Methods

liftParseJSON :: (Value -> Parser a0) -> (Value -> Parser [a0]) -> Value -> Parser (a, b, c, d, e, a0) #

liftParseJSONList :: (Value -> Parser a0) -> (Value -> Parser [a0]) -> Value -> Parser [(a, b, c, d, e, a0)] #

(FromJSON a, FromJSON b, FromJSON c, FromJSON d, FromJSON e, FromJSON f) => FromJSON1 ((,,,,,,) a b c d e f) # 
Instance details

Defined in Data.Aeson.Types.FromJSON

Methods

liftParseJSON :: (Value -> Parser a0) -> (Value -> Parser [a0]) -> Value -> Parser (a, b, c, d, e, f, a0) #

liftParseJSONList :: (Value -> Parser a0) -> (Value -> Parser [a0]) -> Value -> Parser [(a, b, c, d, e, f, a0)] #

(FromJSON a, FromJSON b, FromJSON c, FromJSON d, FromJSON e, FromJSON f, FromJSON g) => FromJSON1 ((,,,,,,,) a b c d e f g) # 
Instance details

Defined in Data.Aeson.Types.FromJSON

Methods

liftParseJSON :: (Value -> Parser a0) -> (Value -> Parser [a0]) -> Value -> Parser (a, b, c, d, e, f, g, a0) #

liftParseJSONList :: (Value -> Parser a0) -> (Value -> Parser [a0]) -> Value -> Parser [(a, b, c, d, e, f, g, a0)] #

(FromJSON a, FromJSON b, FromJSON c, FromJSON d, FromJSON e, FromJSON f, FromJSON g, FromJSON h) => FromJSON1 ((,,,,,,,,) a b c d e f g h) # 
Instance details

Defined in Data.Aeson.Types.FromJSON

Methods

liftParseJSON :: (Value -> Parser a0) -> (Value -> Parser [a0]) -> Value -> Parser (a, b, c, d, e, f, g, h, a0) #

liftParseJSONList :: (Value -> Parser a0) -> (Value -> Parser [a0]) -> Value -> Parser [(a, b, c, d, e, f, g, h, a0)] #

(FromJSON a, FromJSON b, FromJSON c, FromJSON d, FromJSON e, FromJSON f, FromJSON g, FromJSON h, FromJSON i) => FromJSON1 ((,,,,,,,,,) a b c d e f g h i) # 
Instance details

Defined in Data.Aeson.Types.FromJSON

Methods

liftParseJSON :: (Value -> Parser a0) -> (Value -> Parser [a0]) -> Value -> Parser (a, b, c, d, e, f, g, h, i, a0) #

liftParseJSONList :: (Value -> Parser a0) -> (Value -> Parser [a0]) -> Value -> Parser [(a, b, c, d, e, f, g, h, i, a0)] #

(FromJSON a, FromJSON b, FromJSON c, FromJSON d, FromJSON e, FromJSON f, FromJSON g, FromJSON h, FromJSON i, FromJSON j) => FromJSON1 ((,,,,,,,,,,) a b c d e f g h i j) # 
Instance details

Defined in Data.Aeson.Types.FromJSON

Methods

liftParseJSON :: (Value -> Parser a0) -> (Value -> Parser [a0]) -> Value -> Parser (a, b, c, d, e, f, g, h, i, j, a0) #

liftParseJSONList :: (Value -> Parser a0) -> (Value -> Parser [a0]) -> Value -> Parser [(a, b, c, d, e, f, g, h, i, j, a0)] #

(FromJSON a, FromJSON b, FromJSON c, FromJSON d, FromJSON e, FromJSON f, FromJSON g, FromJSON h, FromJSON i, FromJSON j, FromJSON k) => FromJSON1 ((,,,,,,,,,,,) a b c d e f g h i j k) # 
Instance details

Defined in Data.Aeson.Types.FromJSON

Methods

liftParseJSON :: (Value -> Parser a0) -> (Value -> Parser [a0]) -> Value -> Parser (a, b, c, d, e, f, g, h, i, j, k, a0) #

liftParseJSONList :: (Value -> Parser a0) -> (Value -> Parser [a0]) -> Value -> Parser [(a, b, c, d, e, f, g, h, i, j, k, a0)] #

(FromJSON a, FromJSON b, FromJSON c, FromJSON d, FromJSON e, FromJSON f, FromJSON g, FromJSON h, FromJSON i, FromJSON j, FromJSON k, FromJSON l) => FromJSON1 ((,,,,,,,,,,,,) a b c d e f g h i j k l) # 
Instance details

Defined in Data.Aeson.Types.FromJSON

Methods

liftParseJSON :: (Value -> Parser a0) -> (Value -> Parser [a0]) -> Value -> Parser (a, b, c, d, e, f, g, h, i, j, k, l, a0) #

liftParseJSONList :: (Value -> Parser a0) -> (Value -> Parser [a0]) -> Value -> Parser [(a, b, c, d, e, f, g, h, i, j, k, l, a0)] #

(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) => FromJSON1 ((,,,,,,,,,,,,,) a b c d e f g h i j k l m) # 
Instance details

Defined in Data.Aeson.Types.FromJSON

Methods

liftParseJSON :: (Value -> Parser a0) -> (Value -> Parser [a0]) -> Value -> Parser (a, b, c, d, e, f, g, h, i, j, k, l, m, a0) #

liftParseJSONList :: (Value -> Parser a0) -> (Value -> Parser [a0]) -> Value -> Parser [(a, b, c, d, e, f, g, h, i, j, k, l, m, a0)] #

(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) => FromJSON1 ((,,,,,,,,,,,,,,) a b c d e f g h i j k l m n) # 
Instance details

Defined in Data.Aeson.Types.FromJSON

Methods

liftParseJSON :: (Value -> Parser a0) -> (Value -> Parser [a0]) -> Value -> Parser (a, b, c, d, e, f, g, h, i, j, k, l, m, n, a0) #

liftParseJSONList :: (Value -> Parser a0) -> (Value -> Parser [a0]) -> Value -> Parser [(a, b, c, d, e, f, g, h, i, j, k, l, m, n, a0)] #

parseJSON1 :: (FromJSON1 f, FromJSON a) => Value -> Parser (f a) #

Lift the standard parseJSON function through the type constructor.

class FromJSON2 f where #

Lifting of the FromJSON class to binary type constructors.

Instead of manually writing your FromJSON2 instance, Data.Aeson.TH provides Template Haskell functions which will derive an instance at compile time.

Minimal complete definition

liftParseJSON2

Methods

liftParseJSON2 :: (Value -> Parser a) -> (Value -> Parser [a]) -> (Value -> Parser b) -> (Value -> Parser [b]) -> Value -> Parser (f a b) #

liftParseJSONList2 :: (Value -> Parser a) -> (Value -> Parser [a]) -> (Value -> Parser b) -> (Value -> Parser [b]) -> Value -> Parser [f a b] #

Instances
FromJSON2 Either # 
Instance details

Defined in Data.Aeson.Types.FromJSON

Methods

liftParseJSON2 :: (Value -> Parser a) -> (Value -> Parser [a]) -> (Value -> Parser b) -> (Value -> Parser [b]) -> Value -> Parser (Either a b) #

liftParseJSONList2 :: (Value -> Parser a) -> (Value -> Parser [a]) -> (Value -> Parser b) -> (Value -> Parser [b]) -> Value -> Parser [Either a b] #

FromJSON2 (,) # 
Instance details

Defined in Data.Aeson.Types.FromJSON

Methods

liftParseJSON2 :: (Value -> Parser a) -> (Value -> Parser [a]) -> (Value -> Parser b) -> (Value -> Parser [b]) -> Value -> Parser (a, b) #

liftParseJSONList2 :: (Value -> Parser a) -> (Value -> Parser [a]) -> (Value -> Parser b) -> (Value -> Parser [b]) -> Value -> Parser [(a, b)] #

FromJSON a => FromJSON2 ((,,) a) # 
Instance details

Defined in Data.Aeson.Types.FromJSON

Methods

liftParseJSON2 :: (Value -> Parser a0) -> (Value -> Parser [a0]) -> (Value -> Parser b) -> (Value -> Parser [b]) -> Value -> Parser (a, a0, b) #

liftParseJSONList2 :: (Value -> Parser a0) -> (Value -> Parser [a0]) -> (Value -> Parser b) -> (Value -> Parser [b]) -> Value -> Parser [(a, a0, b)] #

FromJSON2 (Const :: Type -> Type -> Type) # 
Instance details

Defined in Data.Aeson.Types.FromJSON

Methods

liftParseJSON2 :: (Value -> Parser a) -> (Value -> Parser [a]) -> (Value -> Parser b) -> (Value -> Parser [b]) -> Value -> Parser (Const a b) #

liftParseJSONList2 :: (Value -> Parser a) -> (Value -> Parser [a]) -> (Value -> Parser b) -> (Value -> Parser [b]) -> Value -> Parser [Const a b] #

FromJSON2 (Tagged :: Type -> Type -> Type) # 
Instance details

Defined in Data.Aeson.Types.FromJSON

Methods

liftParseJSON2 :: (Value -> Parser a) -> (Value -> Parser [a]) -> (Value -> Parser b) -> (Value -> Parser [b]) -> Value -> Parser (Tagged a b) #

liftParseJSONList2 :: (Value -> Parser a) -> (Value -> Parser [a]) -> (Value -> Parser b) -> (Value -> Parser [b]) -> Value -> Parser [Tagged a b] #

(FromJSON a, FromJSON b) => FromJSON2 ((,,,) a b) # 
Instance details

Defined in Data.Aeson.Types.FromJSON

Methods

liftParseJSON2 :: (Value -> Parser a0) -> (Value -> Parser [a0]) -> (Value -> Parser b0) -> (Value -> Parser [b0]) -> Value -> Parser (a, b, a0, b0) #

liftParseJSONList2 :: (Value -> Parser a0) -> (Value -> Parser [a0]) -> (Value -> Parser b0) -> (Value -> Parser [b0]) -> Value -> Parser [(a, b, a0, b0)] #

(FromJSON a, FromJSON b, FromJSON c) => FromJSON2 ((,,,,) a b c) # 
Instance details

Defined in Data.Aeson.Types.FromJSON

Methods

liftParseJSON2 :: (Value -> Parser a0) -> (Value -> Parser [a0]) -> (Value -> Parser b0) -> (Value -> Parser [b0]) -> Value -> Parser (a, b, c, a0, b0) #

liftParseJSONList2 :: (Value -> Parser a0) -> (Value -> Parser [a0]) -> (Value -> Parser b0) -> (Value -> Parser [b0]) -> Value -> Parser [(a, b, c, a0, b0)] #

(FromJSON a, FromJSON b, FromJSON c, FromJSON d) => FromJSON2 ((,,,,,) a b c d) # 
Instance details

Defined in Data.Aeson.Types.FromJSON

Methods

liftParseJSON2 :: (Value -> Parser a0) -> (Value -> Parser [a0]) -> (Value -> Parser b0) -> (Value -> Parser [b0]) -> Value -> Parser (a, b, c, d, a0, b0) #

liftParseJSONList2 :: (Value -> Parser a0) -> (Value -> Parser [a0]) -> (Value -> Parser b0) -> (Value -> Parser [b0]) -> Value -> Parser [(a, b, c, d, a0, b0)] #

(FromJSON a, FromJSON b, FromJSON c, FromJSON d, FromJSON e) => FromJSON2 ((,,,,,,) a b c d e) # 
Instance details

Defined in Data.Aeson.Types.FromJSON

Methods

liftParseJSON2 :: (Value -> Parser a0) -> (Value -> Parser [a0]) -> (Value -> Parser b0) -> (Value -> Parser [b0]) -> Value -> Parser (a, b, c, d, e, a0, b0) #

liftParseJSONList2 :: (Value -> Parser a0) -> (Value -> Parser [a0]) -> (Value -> Parser b0) -> (Value -> Parser [b0]) -> Value -> Parser [(a, b, c, d, e, a0, b0)] #

(FromJSON a, FromJSON b, FromJSON c, FromJSON d, FromJSON e, FromJSON f) => FromJSON2 ((,,,,,,,) a b c d e f) # 
Instance details

Defined in Data.Aeson.Types.FromJSON

Methods

liftParseJSON2 :: (Value -> Parser a0) -> (Value -> Parser [a0]) -> (Value -> Parser b0) -> (Value -> Parser [b0]) -> Value -> Parser (a, b, c, d, e, f, a0, b0) #

liftParseJSONList2 :: (Value -> Parser a0) -> (Value -> Parser [a0]) -> (Value -> Parser b0) -> (Value -> Parser [b0]) -> Value -> Parser [(a, b, c, d, e, f, a0, b0)] #

(FromJSON a, FromJSON b, FromJSON c, FromJSON d, FromJSON e, FromJSON f, FromJSON g) => FromJSON2 ((,,,,,,,,) a b c d e f g) # 
Instance details

Defined in Data.Aeson.Types.FromJSON

Methods

liftParseJSON2 :: (Value -> Parser a0) -> (Value -> Parser [a0]) -> (Value -> Parser b0) -> (Value -> Parser [b0]) -> Value -> Parser (a, b, c, d, e, f, g, a0, b0) #

liftParseJSONList2 :: (Value -> Parser a0) -> (Value -> Parser [a0]) -> (Value -> Parser b0) -> (Value -> Parser [b0]) -> Value -> Parser [(a, b, c, d, e, f, g, a0, b0)] #

(FromJSON a, FromJSON b, FromJSON c, FromJSON d, FromJSON e, FromJSON f, FromJSON g, FromJSON h) => FromJSON2 ((,,,,,,,,,) a b c d e f g h) # 
Instance details

Defined in Data.Aeson.Types.FromJSON

Methods

liftParseJSON2 :: (Value -> Parser a0) -> (Value -> Parser [a0]) -> (Value -> Parser b0) -> (Value -> Parser [b0]) -> Value -> Parser (a, b, c, d, e, f, g, h, a0, b0) #

liftParseJSONList2 :: (Value -> Parser a0) -> (Value -> Parser [a0]) -> (Value -> Parser b0) -> (Value -> Parser [b0]) -> Value -> Parser [(a, b, c, d, e, f, g, h, a0, b0)] #

(FromJSON a, FromJSON b, FromJSON c, FromJSON d, FromJSON e, FromJSON f, FromJSON g, FromJSON h, FromJSON i) => FromJSON2 ((,,,,,,,,,,) a b c d e f g h i) # 
Instance details

Defined in Data.Aeson.Types.FromJSON

Methods

liftParseJSON2 :: (Value -> Parser a0) -> (Value -> Parser [a0]) -> (Value -> Parser b0) -> (Value -> Parser [b0]) -> Value -> Parser (a, b, c, d, e, f, g, h, i, a0, b0) #

liftParseJSONList2 :: (Value -> Parser a0) -> (Value -> Parser [a0]) -> (Value -> Parser b0) -> (Value -> Parser [b0]) -> Value -> Parser [(a, b, c, d, e, f, g, h, i, a0, b0)] #

(FromJSON a, FromJSON b, FromJSON c, FromJSON d, FromJSON e, FromJSON f, FromJSON g, FromJSON h, FromJSON i, FromJSON j) => FromJSON2 ((,,,,,,,,,,,) a b c d e f g h i j) # 
Instance details

Defined in Data.Aeson.Types.FromJSON

Methods

liftParseJSON2 :: (Value -> Parser a0) -> (Value -> Parser [a0]) -> (Value -> Parser b0) -> (Value -> Parser [b0]) -> Value -> Parser (a, b, c, d, e, f, g, h, i, j, a0, b0) #

liftParseJSONList2 :: (Value -> Parser a0) -> (Value -> Parser [a0]) -> (Value -> Parser b0) -> (Value -> Parser [b0]) -> Value -> Parser [(a, b, c, d, e, f, g, h, i, j, a0, b0)] #

(FromJSON a, FromJSON b, FromJSON c, FromJSON d, FromJSON e, FromJSON f, FromJSON g, FromJSON h, FromJSON i, FromJSON j, FromJSON k) => FromJSON2 ((,,,,,,,,,,,,) a b c d e f g h i j k) # 
Instance details

Defined in Data.Aeson.Types.FromJSON

Methods

liftParseJSON2 :: (Value -> Parser a0) -> (Value -> Parser [a0]) -> (Value -> Parser b0) -> (Value -> Parser [b0]) -> Value -> Parser (a, b, c, d, e, f, g, h, i, j, k, a0, b0) #

liftParseJSONList2 :: (Value -> Parser a0) -> (Value -> Parser [a0]) -> (Value -> Parser b0) -> (Value -> Parser [b0]) -> Value -> Parser [(a, b, c, d, e, f, g, h, i, j, k, a0, b0)] #

(FromJSON a, FromJSON b, FromJSON c, FromJSON d, FromJSON e, FromJSON f, FromJSON g, FromJSON h, FromJSON i, FromJSON j, FromJSON k, FromJSON l) => FromJSON2 ((,,,,,,,,,,,,,) a b c d e f g h i j k l) # 
Instance details

Defined in Data.Aeson.Types.FromJSON

Methods

liftParseJSON2 :: (Value -> Parser a0) -> (Value -> Parser [a0]) -> (Value -> Parser b0) -> (Value -> Parser [b0]) -> Value -> Parser (a, b, c, d, e, f, g, h, i, j, k, l, a0, b0) #

liftParseJSONList2 :: (Value -> Parser a0) -> (Value -> Parser [a0]) -> (Value -> Parser b0) -> (Value -> Parser [b0]) -> Value -> Parser [(a, b, c, d, e, f, g, h, i, j, k, l, a0, b0)] #

(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) => FromJSON2 ((,,,,,,,,,,,,,,) a b c d e f g h i j k l m) # 
Instance details

Defined in Data.Aeson.Types.FromJSON

Methods

liftParseJSON2 :: (Value -> Parser a0) -> (Value -> Parser [a0]) -> (Value -> Parser b0) -> (Value -> Parser [b0]) -> Value -> Parser (a, b, c, d, e, f, g, h, i, j, k, l, m, a0, b0) #

liftParseJSONList2 :: (Value -> Parser a0) -> (Value -> Parser [a0]) -> (Value -> Parser b0) -> (Value -> Parser [b0]) -> Value -> Parser [(a, b, c, d, e, f, g, h, i, j, k, l, m, a0, b0)] #

parseJSON2 :: (FromJSON2 f, FromJSON a, FromJSON b) => Value -> Parser (f a b) #

Lift the standard parseJSON function through the type constructor.

class ToJSON1 f where #

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 Generic1 clause to your datatype and declare a ToJSON1 instance for your datatype without giving definitions for liftToJSON or liftToEncoding.

For example:

{-# LANGUAGE DeriveGeneric #-}

import GHC.Generics

data Pair = 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 = map toUpper
                }

instance ToJSON a => ToJSON1 (Pair a) where
    liftToJSON     = genericLiftToJSON customOptions
    liftToEncoding = genericLiftToEncoding customOptions

See also ToJSON.

Minimal complete definition

Nothing

Methods

liftToJSON :: (a -> Value) -> ([a] -> Value) -> f a -> Value #

liftToJSON :: (Generic1 f, GToJSON Value One (Rep1 f)) => (a -> Value) -> ([a] -> Value) -> f a -> Value #

liftToJSONList :: (a -> Value) -> ([a] -> Value) -> [f a] -> Value #

liftToEncoding :: (a -> Encoding) -> ([a] -> Encoding) -> f a -> Encoding #

liftToEncoding :: (Generic1 f, GToJSON Encoding One (Rep1 f)) => (a -> Encoding) -> ([a] -> Encoding) -> f a -> Encoding #

liftToEncodingList :: (a -> Encoding) -> ([a] -> Encoding) -> [f a] -> Encoding #

Instances
ToJSON1 [] # 
Instance details

Defined in Data.Aeson.Types.ToJSON

Methods

liftToJSON :: (a -> Value) -> ([a] -> Value) -> [a] -> Value #

liftToJSONList :: (a -> Value) -> ([a] -> Value) -> [[a]] -> Value #

liftToEncoding :: (a -> Encoding) -> ([a] -> Encoding) -> [a] -> Encoding #

liftToEncodingList :: (a -> Encoding) -> ([a] -> Encoding) -> [[a]] -> Encoding #

ToJSON1 Maybe # 
Instance details

Defined in Data.Aeson.Types.ToJSON

Methods

liftToJSON :: (a -> Value) -> ([a] -> Value) -> Maybe a -> Value #

liftToJSONList :: (a -> Value) -> ([a] -> Value) -> [Maybe a] -> Value #

liftToEncoding :: (a -> Encoding) -> ([a] -> Encoding) -> Maybe a -> Encoding #

liftToEncodingList :: (a -> Encoding) -> ([a] -> Encoding) -> [Maybe a] -> Encoding #

ToJSON1 Min # 
Instance details

Defined in Data.Aeson.Types.ToJSON

Methods

liftToJSON :: (a -> Value) -> ([a] -> Value) -> Min a -> Value #

liftToJSONList :: (a -> Value) -> ([a] -> Value) -> [Min a] -> Value #

liftToEncoding :: (a -> Encoding) -> ([a] -> Encoding) -> Min a -> Encoding #

liftToEncodingList :: (a -> Encoding) -> ([a] -> Encoding) -> [Min a] -> Encoding #

ToJSON1 Max # 
Instance details

Defined in Data.Aeson.Types.ToJSON

Methods

liftToJSON :: (a -> Value) -> ([a] -> Value) -> Max a -> Value #

liftToJSONList :: (a -> Value) -> ([a] -> Value) -> [Max a] -> Value #

liftToEncoding :: (a -> Encoding) -> ([a] -> Encoding) -> Max a -> Encoding #

liftToEncodingList :: (a -> Encoding) -> ([a] -> Encoding) -> [Max a] -> Encoding #

ToJSON1 First # 
Instance details

Defined in Data.Aeson.Types.ToJSON

Methods

liftToJSON :: (a -> Value) -> ([a] -> Value) -> First a -> Value #

liftToJSONList :: (a -> Value) -> ([a] -> Value) -> [First a] -> Value #

liftToEncoding :: (a -> Encoding) -> ([a] -> Encoding) -> First a -> Encoding #

liftToEncodingList :: (a -> Encoding) -> ([a] -> Encoding) -> [First a] -> Encoding #

ToJSON1 Last # 
Instance details

Defined in Data.Aeson.Types.ToJSON

Methods

liftToJSON :: (a -> Value) -> ([a] -> Value) -> Last a -> Value #

liftToJSONList :: (a -> Value) -> ([a] -> Value) -> [Last a] -> Value #

liftToEncoding :: (a -> Encoding) -> ([a] -> Encoding) -> Last a -> Encoding #

liftToEncodingList :: (a -> Encoding) -> ([a] -> Encoding) -> [Last a] -> Encoding #

ToJSON1 WrappedMonoid # 
Instance details

Defined in Data.Aeson.Types.ToJSON

Methods

liftToJSON :: (a -> Value) -> ([a] -> Value) -> WrappedMonoid a -> Value #

liftToJSONList :: (a -> Value) -> ([a] -> Value) -> [WrappedMonoid a] -> Value #

liftToEncoding :: (a -> Encoding) -> ([a] -> Encoding) -> WrappedMonoid a -> Encoding #

liftToEncodingList :: (a -> Encoding) -> ([a] -> Enco