aeson-quick- Quick JSON extractions with Aeson

Safe HaskellNone




aeson-quick is a library for terse marshalling of data to and from aeson's Value.

It works on the observation that by turning objects into tuples inside the Value, the type system can be employed to do more of the work.

For example, given the JSON:

{ "name": "bob"
, "age": 29
, "hobbies": [{"name": "tennis"}, {"name": "cooking"}]

You can write:

extractHobbyist :: Value -> Maybe (String, Int, [String])
extractHobbyist = (.? "{name,age,hobbies:[{name}]}")

(.?) :: FromJSON a => Value -> Structure -> Maybe a Source #

Extracts instances of FromJSON from a Value

This is a wrapper around extract which does the actual work.

Examples assume FromJSON Foo and FromJSON Bar.

Extract key from object:

>>> value .? "{key}" :: Maybe Foo

Extract list of objects:

>>> value .? "[{key}]" :: Maybe [Foo]

Extract with optional key:

>>> value .? "{key,opt?}" :: Maybe (Foo, Maybe Bar)

(.!) :: FromJSON a => Value -> Structure -> a Source #

Unsafe version of .?. Returns error on failure.

extract :: FromJSON a => Structure -> Value -> Parser a Source #

The Parser that executes a Structure against a Value to return an instance of FromJSON.

(.%) :: ToJSON a => Structure -> a -> Value Source #

Turns data into JSON objects.

This is a wrapper around build which does the actual work.

Build a simple Value:

>>> encode $ "{a}" .% True
{\"a\": True}

Build a complex Value:

>>> encode $ "[{a}]" '.%' [True, False]

build :: ToJSON a => Structure -> Value -> a -> Value Source #

Executes a Structure against provided data to update a Value.

Note: Still has undefined behaviours, not at all stable.

parseStructure :: Text -> Either String Structure Source #

Parse a structure, can fail