lens-4.2: Lenses, Folds and Traversals

Copyright(c) Edward Kmett 2013-2014, (c) Paul Wilson 2012
LicenseBSD3
MaintainerEdward Kmett <ekmett@gmail.com>
Stabilityexperimental
Portabilitynon-portable
Safe HaskellTrustworthy
LanguageHaskell98

Data.Aeson.Lens

Contents

Description

 

Synopsis

Numbers

class AsNumber t where Source

Minimal complete definition

Nothing

Methods

_Number :: Prism' t Scientific Source

>>> "[1, \"x\"]" ^? nth 0 . _Number
Just 1.0

>>> "[1, \"x\"]" ^? nth 1 . _Number
Nothing

_Double :: Prism' t Double Source

Prism into an Double over a Value, Primitive or Scientific

>>> "[10.2]" ^? nth 0 . _Double
Just 10.2

_Integer :: Prism' t Integer Source

Prism into an Integer over a Value, Primitive or Scientific

>>> "[10]" ^? nth 0 . _Integer
Just 10

>>> "[10.5]" ^? nth 0 . _Integer
Just 10

>>> "42" ^? _Integer
Just 42

Instances

_Integral :: (AsNumber t, Integral a) => Prism' t a Source

Access Integer Values as Integrals.

>>> "[10]" ^? nth 0 . _Integral
Just 10

>>> "[10.5]" ^? nth 0 . _Integral
Just 10

nonNull :: Prism' Value Value Source

Prism into non-Null values

>>> "{\"a\": \"xyz\", \"b\": null}" ^? key "a" . nonNull
Just (String "xyz")

>>> "{\"a\": {}, \"b\": null}" ^? key "a" . nonNull
Just (Object fromList [])

>>> "{\"a\": \"xyz\", \"b\": null}" ^? key "b" . nonNull
Nothing

Primitive

data Primitive Source

Primitives of Value

Constructors

StringPrim !Text 
NumberPrim !Scientific 
BoolPrim !Bool 
NullPrim 

Instances

class AsNumber t => AsPrimitive t where Source

Minimal complete definition

Nothing

Methods

_Primitive :: Prism' t Primitive Source

>>> "[1, \"x\", null, true, false]" ^? nth 0 . _Primitive
Just (NumberPrim 1.0)

>>> "[1, \"x\", null, true, false]" ^? nth 1 . _Primitive
Just (StringPrim "x")

>>> "[1, \"x\", null, true, false]" ^? nth 2 . _Primitive
Just NullPrim

>>> "[1, \"x\", null, true, false]" ^? nth 3 . _Primitive
Just (BoolPrim True)

>>> "[1, \"x\", null, true, false]" ^? nth 4 . _Primitive
Just (BoolPrim False)

_String :: Prism' t Text Source

_Bool :: Prism' t Bool Source

_Null :: Prism' t () Source

Instances

Objects and Arrays

class AsPrimitive t => AsValue t where Source

Minimal complete definition

Nothing

Methods

_Value :: Prism' t Value Source

>>> "[1,2,3]" ^? _Value
Just (Array (fromList [Number 1.0,Number 2.0,Number 3.0]))

_Object :: Prism' t (HashMap Text Value) Source

>>> "{\"a\": {}, \"b\": null}" ^? key "a" . _Object
Just fromList []

>>> "{\"a\": {}, \"b\": null}" ^? key "b" . _Object
Nothing

>>> _Object._Wrapped # [("key" :: Text, _String # "value")] :: String
"{\"key\":\"value\"}"

_Array :: Prism' t (Vector Value) Source

>>> "[1,2,3]" ^? _Array
Just (fromList [Number 1.0,Number 2.0,Number 3.0])

Instances

key :: AsValue t => Text -> Traversal' t Value Source

Like ix, but for Object with Text indices. This often has better inference than ix when used with OverloadedStrings.

>>> "{\"a\": 100, \"b\": 200}" ^? key "a"
Just (Number 100.0)

>>> "[1,2,3]" ^? key "a"
Nothing

members :: AsValue t => IndexedTraversal' Text t Value Source

An indexed Traversal into Object properties

"{\"a\": 4, \"b\": 7}" ^@.. members
("a",Number 4.0),("b",Number 7.0)
"{\"a\": 4, \"b\": 7}" & members . _Number *~ 10

"{"a":40,"b":70}"

nth :: AsValue t => Int -> Traversal' t Value Source

Like ix, but for Arrays with Int indexes

>>> "[1,2,3]" ^? nth 1
Just (Number 2.0)

>>> "\"a\": 100, \"b\": 200}" ^? nth 1
Nothing

>>> "[1,2,3]" & nth 1 .~ Number 20
"[1,20,3]"

values :: AsValue t => IndexedTraversal' Int t Value Source

An indexed Traversal into Array elements

>>> "[1,2,3]" ^.. values
[Number 1.0,Number 2.0,Number 3.0]

>>> "[1,2,3]" & values . _Number *~ 10
"[10,20,30]"

Decoding

class AsJSON t where Source

Minimal complete definition

Nothing

Methods

_JSON :: (FromJSON a, ToJSON a) => Prism' t a Source

_JSON is a Prism from something containing JSON to something encoded in that structure

Instances