How to write forms?

To write an HTML form towards an Eliom service

Just as we do for links, we provide form-building functions that call Eliom services in a safe manner. These functions are provided in the module Eliom_content.​Html.​D.​Form (and Eliom_content.​Html.​F.​Form). The functions Eliom_content.​Html.​D.​Form.​get_form and Eliom_content.​Html.​D.​Form.​post_form accept a function (named create_form in our example below) which is responsible for generating the content from appropriately-typed parameter names.

Here a complete example.

  open Eliom_parameter
  open Eliom_content.Html.D
(* Create the form with some inputs *)
let%server create_form =
  (fun (number_name, (number2_name, string_name)) ->
    [p [pcdata "Write an int: ";
          ~input_type:`Text ~name:number_name
        pcdata "Write another int: ";
          ~input_type:`Text ~name:number2_name
        pcdata "Write a string: ";
        Form.input ~input_type:`Text ~name:string_name Form.string;
        Form.input ~input_type:`Submit ~value:"Click" Form.string]])

let%server form_result_service = Eliom_service.create
  ~path:(Eliom_service.Path ["form-result"])
  ~meth:(Eliom_service.Get ((int "number_name") ** ((int "number2_name") ** (string "string_name"))))

let%server form_result_handler =
  (fun (number_name, (number2_name, string_name)) () ->
     Lwt.return (
          (head (title (pcdata "")) [])
          (body [
             p [
               pcdata "First number: ";
               pcdata (string_of_int number_name);
             p [
               pcdata "Second number: ";
               pcdata (string_of_int number2_name);
             p [
               pcdata "String: ";
               pcdata string_name

let%server form_service = Eliom_service.create
  ~path:(Eliom_service.Path ["form"])
  ~meth:(Eliom_service.Get unit)

let%server form_handler =
  (fun () () ->
     let form = Form.get_form ~service:form_result_service create_form in
         (head (title (pcdata "Form example")) [])
         (body [form])))

let%server () =
  Eliom_registration.Html.register ~service:form_result_service form_result_handler;
  Eliom_registration.Html.register ~service:form_service form_handler

As shown in the example, Eliom_content.​Html.​D.​Form provides functions for generating the various widgets, e.g., Eliom_content.​Html.​D.​Form.​input. These functions need to be called with a "type" argument (e.g., Eliom_content.​Html.​D.​Form.​int) that matches the type of the corresponding parameter name.

POST forms may also take get parameters, as last argument of function post_form:

  (fun my_string ->
    p [pcdata "Write a string: ";
       Form.input ~input_type:`Text ~name:my_string Form.string])

Raw forms

There is also a raw interface to write basic forms without Eliom, using standard tyxml constructors.

Use module Eliom_content.Html.D.Raw.