I get that I need formlet-process somewhere, but what I wanted is to only
know about it in the same function/closure where I am doing the rendering -
which obviously works in the definition of embed-formlet above, since it
embeds the url to format-process. I thought that embed-formlet would
somehow store formlet-process in some table somewhere and then make it
available in some shape once the URL gets hit, but now I see it's a simple
closure.
What I want to achieve seems to be done by the following code:
(define (debrief request)
(define test-formlet
(formlet
(div "Name:" ,{input-string . => . name})
(list name)))
(define (response-generator embed/url)
(html-wrapper
`((h1 "Testing Formlets")
,(embed-formlet embed/url test-formlet)
)))
(define (testing result)
(html-wrapper
`((h1 "Result")
(div
,(first result)))))
(testing (send/suspend/dispatch response-generator)))
with the exception that I want a submit button inside the form element, but
that should be easy enough to solve. In short, I wanted to have the
function `testing` to not need to be passed the formlet I defined, yet to
receive the results.
Thanks for solving the problem I had, if not the problem I stated.
Cheers,
Marc
On Wed, Aug 23, 2017 at 3:39 PM, Jay McCarthy <jay.mccar...@gmail.com>
wrote:
> On Wed, Aug 23, 2017 at 8:26 AM, Marc Kaufmann
> <marc.kaufman...@gmail.com> wrote:
> > Hi again,
> >
> > I am now trying to deal with formlets in a more principled fashion and
> thus
> > trying to implement, as Philip suggested, to use `send/formlet` and
> > `embed-formlet`. After a lot of tinkering, I still haven't figured out
> how
> > to actually process the formlet (without having to pass it around) with
> > embed-formlet. Here is the current example:
> >
> > (define (debrief request)
> > (define test-formlet
> > (formlet
> > (div "Name:" ,{input-string . => . name})
> > (list name)))
> > (define (response-generator embed/url)
> > (html-wrapper
> > `((h1 "Testing Formlets")
> > (form ([action ,(embed/url testing)]
> > [method "POST"])
> > (p "Here is the displayed formlet")
> > ;,@(formlet-display test-formlet) ;; THIS WORKS
> > ,(embed-formlet embed/url test-formlet)
> > (input ([type "submit"]))
> > ))))
> >
> > The above works without `embed-formlet` with the following definition of
> > `testing`:
> >
> > (define (testing request)
> > (define result (formlet-process test-formlet request))
> > (html-wrapper
> > `((h1 "Result")
> > (div
> > ,(first result)))))
> > (send/suspend/dispatch response-generator))
> >
> > But it does not work (or I can't figure out how it works) with
> > embed-formlet. How do I process the formlet, with the requirement that I
> do
> > not want to refer explicitly to `test-formlet`?
>
> That is not possible. A formlet defines two things: the rendering and
> the processing, so it doesn't make sense to process without the
> processing definition.
>
> > Or is this not possible - in
> > which case, what does `embed-formlet` do that `formlet-processing`
> doesn't?
> > Any working example with embed-formlet is appreciate, even if it is not
> the
> > same as mine.
>
> When you use embed-formlet, the formlet is displayed and when you
> submit, then the formlet's processing runs and returns to the
> call-site of send/suspend/dispatch. So you don't separate them.
> embed-formlet is really simple:
>
> (define (embed-formlet embed/url f)
> `(form ([action ,(embed/url
> (lambda (r)
> (formlet-process f r)))])
> ,@(formlet-display f)))
>
> > Thanks,
> > Marc
> >
> >
> > On Thu, Mar 16, 2017 at 2:11 PM, Marc Kaufmann <
> marc.kaufman...@gmail.com>
> > wrote:
> >>
> >> Thanks Philip. I checked out the links, but I fear that it's over my
> head,
> >> and that I would almost surely screw it up. For now I'll keep passing
> the
> >> parameters.
> >>
> >> Cheers,
> >> Marc
> >>
> >> On Tuesday, March 14, 2017 at 3:22:39 PM UTC-4, Philip McGrath wrote:
> >> > If you want it to be part of the continuation without having to pass
> it
> >> > around as an argument, check out web cells
> >> > (http://docs.racket-lang.org/web-server/stateless.html?q=
> web-server%2Flang%2Fwe#%28mod-path._web-server%2Flang%2Fweb-cells%29)
> >> > or web parameters
> >> > (http://docs.racket-lang.org/web-server/stateless.html?q=
> web-server%2Flang%2Fwe#%28mod-path._web-server%2Flang%2Fweb-param%29).
> >> >
> >> >
> >> >
> >> > -Philip
> >> >
> >> >
> >> >
> >> > On Tue, Mar 14, 2017 at 1:48 PM, Marc Kaufmann <marc.ka...@gmail.com>
> >> > wrote:
> >> >
> >> >
> >> >
> >> > Thanks for the detailed answer Philip! Some of it is definitely over
> my
> >> > head. The reason I don't pass around the id is that I use the html
> field
> >> > exactly to track the id and wanted to avoid having to pass around the
> >> > argument left and right - and the only ways to pass it on are via
> forms or
> >> > by sticking it into the requested URL or by using continuations. I
> will give
> >> > the continuation-style solution a shot though, it's probably cleaner
> to pass
> >> > the id around as an argument.
> >> >
> >> > Cheers,
> >> > Marc
> >> >
> >> >
> >> >
> >> >
> >> >
> >> > On Tue, Mar 14, 2017 at 1:34 PM, Philip McGrath
> >> > <phi...@philipmcgrath.com> wrote:
> >> >
> >> > In this case it will work despite being a hack, because you know that
> >> > your id argument affects only the display stage, not the processing
> stage:
> >> > however, you can't know in general that this will work for dynamically
> >> > generated formlets, and personally I would therefore be reluctant to
> rely on
> >> > this, both because it is fragile in terms of changes to your
> implementation
> >> > of matrix-formlet that you might make later.
> >> >
> >> >
> >> > If you are using native continuations (i.e. not the stateless #lang
> >> > web-server), you can use send/formlet or embed-formlet to deal with
> this
> >> > correctly and easily. (At a lower level, you could also do something
> >> > like(define-values (xexpr-forest bindings->result i)
> >> > ((matrix-formlet "3") 0))
> >> > to access the low-level rendering, processing function, and next
> >> > allowable input integer directly.)
> >> >
> >> >
> >> > It is a little more tricky in #lang web-server, because your formlet
> and
> >> > it's generated processing function are plain functions, and thus not
> >> > serializable (see this old thread for discussion:
> >> > https://groups.google.com/d/topic/racket-users/lMYWjodgpmo/discussion).
> The
> >> > easy work-around is to keep the arguments you need to reproduce your
> formlet
> >> > around as part of the closure, e.g. by rewriting your
> matrix-submission like
> >> > this:(define (matrix-submission req id)
> >> > (define-values (number-of-ones user-id)
> >> > (formlet-process (matrix-formlet id) req))
> >> > ...)
> >> > The alternative is to either recompile the formlet library using #lang
> >> > web-server/base or to implement your formlet at a low level using
> >> > serial-lambda and not use any of the library tools.
> >> >
> >> >
> >> > In this specific case, though, if you are using this hidden input
> field
> >> > just to remember the user id from one request to the next (i.e. you
> wouldn't
> >> > ever change it on the client side with JavaScript or something), the
> best
> >> > solution is not to put it in the form at all, but have it be part of
> the
> >> > continuation. This could also have security advantages, if you
> >> > cryptographically sign your continuations or store them on the
> server. If
> >> > that works for your use case, you could simply write:
> >> > (define matrix-formlet
> >> >
> >> > input-string)
> >> > display it with
> >> > (matrix-submission
> >> > (send/suspend
> >> > (λ (k-url)
> >> > (response/xexpr
> >> > `(html (body (form
> >> > ((action "/the-matrix-submitted")
> >> > (method "post"))
> >> > ,@(formlet-display matrix-formlet)
> >> > (input ([type "submit"]))))))))
> >> > user-id)
> >> > and then define matrix-submission as(define (matrix-submission req
> >> > user-id)
> >> > (define number-of-ones
> >> > (formlet-process matrix-formlet req))
> >> > ...)
> >> >
> >> >
> >> >
> >> > -Philip
> >> >
> >> >
> >> >
> >> >
> >> >
> >> > On Tue, Mar 14, 2017 at 12:01 PM, Marc Kaufmann <marc.ka...@gmail.com
> >
> >> > wrote:
> >> >
> >> >
> >> > Hi,
> >> >
> >> >
> >> >
> >> > I have created a formlet like so:
> >> >
> >> >
> >> >
> >> > (define (matrix-formlet id)
> >> >
> >> > (formlet
> >> >
> >> > (#%# ,{input-string . => . ones}
> >> >
> >> > ,{(to-string (required (hidden id))) . => . user-id}
> >> >
> >> > )
> >> >
> >> > (values ones user-id)))
> >> >
> >> >
> >> >
> >> > I display this as follows:
> >> >
> >> >
> >> >
> >> > `(form
> >> >
> >> > ((action "/the-matrix-submitted")
> >> >
> >> > (method "post"))
> >> >
> >> > ,@(formlet-display (matrix-formlet user-id))
> >> >
> >> > (input ([type "submit"]))))
> >> >
> >> >
> >> >
> >> > and process it like this:
> >> >
> >> >
> >> >
> >> > (define (matrix-submission req)
> >> >
> >> > (define-values (number-of-ones user-id)
> >> >
> >> > (formlet-process (matrix-formlet "3") req))
> >> >
> >> > ...)
> >> >
> >> >
> >> >
> >> > While this works, the formlet I use to display and process are not
> >> > really the same, since they are created on the spot, and created with
> >> > different parameters. So far it seems to work, but I am worried that
> this
> >> > will break down, and clearly this isn't the right way to go about
> creating
> >> > parametrizable formlets.
> >> >
> >> >
> >> >
> >> > The questions are (i) is the above going to work despite being a hack,
> >> > and (ii) is there a correct and easy way to do the same thing?
> >> >
> >> >
> >> >
> >> > Cheers,
> >> >
> >> > Marc
> >> >
> >> >
> >> >
> >> > --
> >> >
> >> > You received this message because you are subscribed to the Google
> >> > Groups "Racket Users" group.
> >> >
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> >> > an email to racket-users...@googlegroups.com.
> >> >
> >> > For more options, visit https://groups.google.com/d/optout.
> >>
> >
> > --
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>
>
>
> --
> -=[ Jay McCarthy http://jeapostrophe.github.io ]=-
> -=[ Associate Professor PLT @ CS @ UMass Lowell ]=-
> -=[ Moses 1:33: And worlds without number have I created; ]=-
>
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