Module type Tick.KV

module type KV = sig .. end

The type for mutable key-value stores.

KV provides access to typed and named values.

Value codecs

type 'a codec = ('a -> string) * (string -> ('a, Rresult.R.msg) Rresult.result)

The type for value codecs. An encoder and a decoder.

exception Decode_error of string * Rresult.R.msg

The exception for key value decode errors. If

Decode (key,
      msg)

is raised it means that the store's data for key could not be decoded using the client's codec. This exception is not meant to be handled by programs, it indicates a configuration mismatch between the program and its environment.

Keys

type 'a key

The type for keys with values of type 'a.

val key : string -> 'a codec -> 'a key

key name codec is a key with lookup name name and whose value is codec'd by codec.

val key_name : 'a key -> string

key_name k is k's name.

val key_codec : 'a key -> 'a codec

key_codec k is k's codec.

val mem : 'a key -> bool

mem k is true iff k is bound to a value of type 'a in the key-value store.

val find : 'a key -> 'a option

find k is k's binding in the key-value store (if any).
Raises Decode_error in case of value decode error.

val get : ?absent:'a -> 'a key -> 'a

get k is k's binding the key-value store. If absent is specified this value is returned if k is not bound in the store.
Raises

Invalid_argument if k is unbound in the key-value store and absent is not specified. TODO maybe unify that with Decode_error.
Decode_error in case of value decode error.

val set : 'a key -> 'a option -> unit

set k v sets the key value of k to v.

Watching keys

type watcher

The type for key-value binding change watchers.

val watch : 'a key -> ('a key -> 'a option -> unit) -> watcher

watch k f is a key-value watcher such that whenever key is Tick.KV.set to v, f k v is called.

val unwatch : watcher -> unit

unwatch w stops the watcher w. After that call it's callback is guaranteed not to be called again.