Module `Ocsipersist.Store_json`

Type-safe variable store using Deriving_Json for serialisation. Unlike Store, this does not rely on Stdlib.Marshal and is safe across OCaml versions. Requires types annotated with [@@deriving json] (from js_of_ocaml-ppx_deriving_json).

Note: The dependency on js_of_ocaml is only for the Deriving_Json runtime library, which provides type-safe JSON serialisation. This is the same serialisation mechanism used by Eliom for client-server communication. No JavaScript compilation is involved.

type 'a t

Type of persistent data

type store

Data are divided into stores. Create one store for your project, where you will save all your data.

val open_store : string -> store Lwt.t

Open a store (and create it if it does not exist)

val make_persistent : 
  store:store ->
  name:string ->
  json:'a Deriving_Json.t ->
  default:'a ->
  'a t Lwt.t

make_persistent ~store ~name ~json ~default find a persistent value named name in store store from database, or create it with the default value default if it does not exist. Uses Deriving_Json for type-safe serialisation. An existing value that cannot be deserialised with json is left in place: reading it with get then fails with Ocsipersist_lib.Decoding_error, and the caller decides whether to overwrite it with set.

val make_persistent_lazy : 
  store:store ->
  name:string ->
  json:'a Deriving_Json.t ->
  default:(unit -> 'a) ->
  'a t Lwt.t

Same as make_persistent but the default value is evaluated only if needed

val make_persistent_lazy_lwt : 
  store:store ->
  name:string ->
  json:'a Deriving_Json.t ->
  default:(unit -> 'a Lwt.t) ->
  'a t Lwt.t

Lwt version of make_persistent_lazy.

val get : 'a t -> 'a Lwt.t

get pv gives the value of pv. Fails with Ocsipersist_lib.Decoding_error if the stored value cannot be deserialised by the codec pv was opened with.

val set : 'a t -> 'a -> unit Lwt.t

set pv value sets a persistent value pv to value