type op_args = {
      cgi : Netcgi.cgi;
      db : Db.db;
      echo : (string -> unit);
      login : (User.login);
      ...
};;

type operation = {
      module_name : string;
      function_name : string;
      func : op_args -> unit;
};;

(* List reference, to be updated by modules at init *)
let op_list = ref ([] : operation list);;

let add_op_login module_name op_name func =
      let op = {
            module_name = module_name;
            function_name = op_name;
            func = (fun args ->
                  match args.login with
                        User.Logged_in user ->
                              func args user
                        | User.Not_logged_in -> args.echo "Please login");
      } in
      add_op op op_list;;

let open Operation in
(*  Old way
let op_args = {
        cgi = cgi;
        db = db;
        echo = echo;
        login = login;
        addr = addr;
        websocket_timeout = websocket_timeout;
        log = (fun s  -> log s);
} in
*)
let op_args = object
        method cgi = cgi
        method db = db
        method echo = echo
        method login = login
        method addr = addr
        method websocket_timeout = websocket_timeout
        method log = (fun s -> log s)
end in

if (op_name <> "" && module_name <> "") then dispatch_op module_name op_name op_args;


Since there's always only one instance of op_args, i want to replace it with an immediate object, if possible. Sometimes I add variables to op_args, and I would like to add it to only one place in the code, instead of as with a record modify both type definition and instance creation.