This package introduces a PPX (Preprocessor Extension) for OCaml that automates the generation of serialization and deserialization functions for your OCaml types using ATD without creating an ATD file.
Currently supporting JSON derivation only:
json_string_of_t: Serializes an OCaml value to a JSON string.t_of_json_string: Deserializes a JSON string back into an OCaml value.
type my_type = {
field1: string;
field2: int;
} [@@deriving atd_j]
(* Serialization *)
let my_value = { field1 = "value1"; field2 = 123 }
let json_string = json_string_of_my_type my_value (* {"field1":"value1","field2":123} *)
(* Deserialization *)
let deserialized_value = my_type_of_json_string json_string
Annotating a record field with [@default v] will allow the generated reader to give default value for the field (and so the field no longer have an optional type). Note v must be in a stringify form: "999" instead of 999.
type my_type = {
field1: string;
field2: int [@default "999"];
} [@@deriving atd_j]
(* Deserialization *)
let deserialized_value = my_type_of_json_string {|{"field1":"value1"}|}
(* { field1 = "value1"; field2 = 999 } *)
All option typed fields are "optional" by default, i.e. if the value is None, it will not be included when serialization and when deserializing, ATD will assume the value is None if the field is not present.
Annotating a record field with [@required] will always keep the optional value in the serialized record and ATD will keep looking for it when deserializing the records.
type my_type = {
field1: string option;
field2: int option [@required];
} [@@deriving atd_j]
(* Serialization *)
let my_value = { field1 = None; field2 = None }
let json_string = json_string_of_my_type my_value (* {"field2":"None"} *)
(* Deserialization *)
let deserialized_value = my_type_of_json_string "{}"
(* Fatal error: exception Atdgen_runtime.Oj_run.Error("Line 1:\nMissing record field field2") *)