[plt-scheme] Parameters and servlets

On 2/16/06, Jens Axel Søgaard <jensaxel at soegaard.net> wrote:
>
> Thanks for the explanation. Your web-cells might do the trick.
>
> I am trying to make a small library that uses site-wide defaults.
> E.g in "view.scm" I'd like to write
>
>    (require "html.scm")
>
>    ;;;
>    ;;; SITE WIDE DEFAULTS
>    ;;;
>
>    (current-page-title       "Foo 2.0")
>    (current-page-header      '(h1 ((class "page_header")) "Foo 2.0!"))
>    (current-page-style-sheet "http://localhost/stylesheet.css")
>
>    (define (html-a-page)
>      (html-page #:body  "Foo bar baz"))
>
> where html-page is defined "html.scm".


For a given site, I typically wrap the 'start' procedure in the site-wide
defaults:

(define (start ir)
 (parameterize ([current-page-title "Foo 2.0"])
  (html-a-page)))

Parameters will work in the web-server provided you are only using
'parameterize', but not if you are using the parameter-procedure set method.

I think this approach is most what you want, as cells do something
different, and your `persistent parameters' seem very kludgy

Jay


At the same time, I want the ability to override the defaults
> for a single request in "control.scm" with, say,
>
>    (parameterize ([current-page-title "Foo 3.0"])
>      (html-a-page))
>
> Apart from the losing the settings when a new thread is started,
> it works nicely.
>
>
> Here is html.scm:
>
> (module html mzscheme
>    (provide (all-defined))
>
>    (require (lib "kw.ss"))
>
>    (define current-page-title        (make-parameter "A title"))
>    (define current-page-header       (make-parameter '(h1 "A Header")))
>    (define current-page-body         (make-parameter "A body"))
>    (define current-page-content-type
>       (make-parameter "text/html;charset=UTF-8"))
>    (define current-page-style-sheet  (make-parameter ""))
>
>    ; html-page
>    ;   Puts all the pieces together to make a complete html page.
>    ;   Defaults are taken from site-wide parameters
>    (define/kw
>      (html-page #:key
>                 (title         (current-page-title))
>                 (title-atts    #f)
>                 (header        (current-page-header))
>                 (head-atts     #f)
>                 (body          (current-page-body))
>                 (body-atts     #f)
>                 (style-sheet   (current-page-style-sheet))
>                 (content-type  (current-page-content-type)))
>      (let ([title-atts (if title-atts (list title-atts) '())]
>            [head-atts  (if head-atts  (list head-atts)  '())]
>            [body-atts  (if body-atts  (list body-atts)  '())])
>        `(html (head  (title , at title-atts ,title)
>                      ; external stylesheet
>                      (link ((rel "stylesheet")
>                             (type "text/css")
>                             (href ,style-sheet)))
>                      (meta ((http-equiv "Content-Type")
>                             (content ,content-type)))
>                      , at head-atts)
>               (body , at body-atts
>                     ,header
>                     ,body))))
>


--
Jay McCarthy <jay at cs.brown.edu>
http://jay.makeoutcity.com/
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