resto 1.2 · OCaml Package

Query parameters are the key-value pairs that appear as ?key0=value0&key1=value1&.. at the end of the path in URIs/URLs.

type 'a t

A type for representing query parameters.

type 'a query = 'a t

val empty : unit query

empty is for services that expects no query parameters.

type ('a, 'b) field

The type for key-value pairs that constitute a query. The first type parameter is for whole-query store and the second is for the type of value carried by the field.

val field : 
  ?descr:string ->
  string ->
  'a Arg.t ->
  'a ->
  ('b -> 'a) ->
  ('b, 'a) field

field ?descr key arg default get is a field for the query parameters, i.e., it describes one key-value pair.

The key is given by key and the value is parsed as specified in arg or, if absent from the URI suffix, default.

Finally, get is for retrieving the value from the whole-query store. More on the whole-query store below.

val opt_field : 
  ?descr:string ->
  string ->
  'a Arg.t ->
  ('b -> 'a option) ->
  ('b, 'a option) field

val flag : ?descr:string -> string -> ('b -> bool) -> ('b, bool) field

val multi_field : 
  ?descr:string ->
  string ->
  'a Arg.t ->
  ('b -> 'a list) ->
  ('b, 'a list) field

type ('a, 'b, 'c) open_query

Queries are constructed by adding fields to an open query and sealing it into a query. This is done using the functions below. Typically, it is done as follow: query c |+ field1 |+ field2 |> seal

As the types require, you must provide the correct argument to the successive building steps. Here is an example: query (fun timeout shade -> (timeout, shade)) |+ field "timeout" Arg.float 10. (fun (timeout, _) -> timeout) |+ field "shade" Arg.string "fuchsia" (fun (_, shade) -> shade) |> seal

The initial query function takes a whole-query store builder (a function that assemble all the fields into a single store of values), and each field takes a function to recover the value from the whole-query store.

val query : 'b -> ('a, 'b, 'b) open_query

val (|+) : 
  ('a, 'b, 'c -> 'd) open_query ->
  ('a, 'c) field ->
  ('a, 'b, 'd) open_query

val seal : ('a, 'b, 'a) open_query -> 'a t

package resto