[Bese-devel] forms (again)

[Marco Baringer]

i've been doing working on some very form intensive componets lately,
due to absurd (as far as i'm concerned) requests an the client's part
i can't just just out generate these so i find myself doing a lot of:

(defclass form ()
  ((form-slot :accessor form-slot)
   (slot :accessor slot))
  (:metaclass standard-component-class))

(defmethod (setf form-slot) (string (f form))
  (setf (slot f) (parse-the-string string)))

(defmethod form-slot ((f form))
  (convert-to-form-string (slot f)))

things get worse when you try to have a single slot in a
form-component which is draw with multiple input tags in the html
(example: dates which are handled by 3 select/option form
fields). this is getting unmanagebale. the issue is that we get text
from the user but we really want are lisp objects, i've got a couple
options which i've tried:

------------------------------

(defclass form ()
  ((slot :accessor slot :form-type float)
   (other-slot :accessor slot :form-type date))
  (:metaclass form-component-class))

the new :form-type slot option would specify:

1) how to transform the slot's value into a string suitable for
   input's value attribute.

2) how to convert the string sent along the wire to a lisp object.

3) an as yet undecided form validation thingy.

4) a method on the generic accessor FORM-VALUE (which is what you'd
   use in :accessor (yaclml) and ucw:accessor (tal) attributes.

------------------------------

the other option is to just write a macro (what i'm currently doing)
so you'd do something along these lines:

(defform form ()
  (slot float))

it's basically the same thing, less typing and less control (and a lot
_more_ typing when you need that little bit of extra control (which
turns out to be way too often)).

i've a couple question which would love answers:

1) is the macro solution that much better than the metaclass solution
   (the metaclass solution is more verbose but cleaner)?

2) is there some other route i'm missing?

------------------------------

this is the least-possible-change solution:

(defclass form ()
  ((slot :accessor slot :component input-text)
   (other-slot :accessor slot :componet input-date)))

however this means you'll still need to write a good bit of munging
code when working with the slots' values. this also entails making
just about every form field be a component, which is a fair amount of
overhead for not much gain.

------------------------------

i keep coming back to this issue and nothing i come up with ever
satisfies me. suggestions? is there something i could steal from
CLIM's presentation types and input streams?

-- 
-Marco
Ring the bells that still can ring.
Forget your perfect offering.
There is a crack in everything.
That's how the light gets in.
     -Leonard Cohen