Json Driver

Json Driver

The Json driver maps to and from Yojson.Safe.t.

The opam package for the driver is ppx_protocol_conv_json.

Options

Standard options mimics that of ppx_deriving_yojson, except that Constructors without arguments are serialized to a string rather than a list.

To set options to create a driver compatible with ppx_deriving_yojson use

open Protocol_conv_json 
module Yojson = Json.Make(
  struct
    include Ppx_protocol_driver.Default_parameters
    let singleton_constr_as_string = false
    let omit_default_values = true
  end : Ppx_protocol_driver.Parameters)

The module Json.Yojson provides a module with the above parameters set for convenience. For speed comparison, see the benchmarks page.

See Parameters for a description of possible options.

Types

Ocaml type	Generates	Accepts
string, char,bytes	`String	`String
int, int32, int64	`Int	`Int
nativeint	`Int	`Int
float	`Float	`Float
bool	`Bool	`Bool
unit	`List []	`List []
'a list, 'a array	`List 'a list	`List 'a list
'a option	`Null or 'a	`Null or 'a
'a ref, lazy 'a	'a	'a
Json.t	Yojson.Safe.t	Yojson.Safe.t

Notes

Serialization differs from ppx_deriving_yojson when serializing in that constructors without arguments are serialized to strings, rather than a list. Constructors with arguments are serialized to lists.

This allows for deserialising a string directly into a ADT:

type country = Denmark | France
and t = {
  name: string;
  country: country;
}  [@@deriving protocol ~driver:(module Json)]

{ name = "Anders"; country = Denmark } |> to_json |> Yojson.Safe.to_string

produces: { "name": "Anders", "country": "Denmark" }