[racket] passing a list of dispatch clauses to dispatch-rules

Just realized I can the desired behavior by just putting the (string-arg)
as the last clause:

(define-values (url-based-dispatch url-generator)
  (dispatch-rules
   [("home") display-home]
   [("some-app") run-app]
   [((string-arg)) dispatch-static-html]))

I'm still curious though whether it's possible to skip to the next clause
by calling next-dispatcher within one dispatch function. The discussion at
http://lists.racket-lang.org/users/archive/2013-September/059728.html
made me think this was possible. In that example, I thought that when
"funny-fish.png" is matched and fail-to-fs throws next-dispatcher that the
idea was for the program to keep trying with the rest of the clauses in the
dispatch rules.

Tobias


On 17 December 2013 17:25, Janos Tobias Locsei <jtlocsei at cantab.net> wrote:

> Hi Jay, I tried again using serve/servelet. This is my full code:
>
> #lang racket
>
> (require web-server/dispatch ; for dispatch-rules
>          web-server/dispatchers/dispatch ; for next-dispatcher
>          web-server/servlet-env ; for serve/servlet
>          web-server/http ; for response/xexpr
>          )
>
> (define-values (url-based-dispatch url-generator)
>   (dispatch-rules
>    [((string-arg)) dispatch-static-html]
>    [("home") display-home]
>    [("some-app") run-app]))
>
> (define (dispatch-static-html request a-path-string)
>   (display "Entered dispatch-static-html\n")
>   ; This will eventually have code to search for static html
>   ; files and display them. For now, just pretend we couldn't find
>   ; the relevant html file so we throw next-dispatcher.
>   (next-dispatcher))
>
> (define (display-home request)
>   (display "Entered display-home\n")
>   (response/xexpr
>    `(html
>      (head (title "Home"))
>      (body (h1 "Home")
>            (p "Welcome to the home page")))))
>
> (define (run-app request)
>   (display "Entered run-app\n")
>   (response/xexpr
>    `(html
>      (head (title "App"))
>      (body (h1 "App")
>            (p "This app is actually just a static page")))))
>
>
> (define (respond-unknown request)
>   (display "Entered respond-unknown\n")
>   (response/xexpr
>    `(html
>      (head (title "Unknown Reponse"))
>      (body (h1 "Unknown Response")
>            (p "Sorry, I couldn't find what you're looking for")))))
>
> (serve/servlet
>  url-based-dispatch ; answers requests
>  #:servlet-path "/home" ; default url
>  #:servlet-regexp #rx"" ; capture all top-level requests
>  #:file-not-found-responder respond-unknown)
>
> What I was expecting (and wanting) was that for the URL "
> http://localhost:8000/home" the function dispatch-static-html would be
> called (because it matches any URL), it would throw next-dispatcher, and
> then display-home would be called, since it's the next matching clause.
>
> But in reality when dispatch-static-html throws next-dispatcher the
> program jumps straight to respond-unknown, which I specified as the
> file-not-found-responder keyword argument when I called serve/servlet.
>
> What am I missing? Is there a way to get the program to do what I wanted
> it to?
>
> Thanks for all your time with this.
>
> Tobias
>
>
>
>
> -------------------------------
>
>
> Thanks Jay, that makes sense. I was testing it without using
> serve/servlet, using the example on
> http://docs.racket-lang.org/web-server/dispatch.html
>
> I will try again using serve/servlet.
>
>
> On 17 December 2013 14:45, Jay McCarthy <jay.mccarthy at gmail.com> wrote:
>
>> The first one is what I would write, except that I'd put it after the
>> ["" ...] case so it doesn't shadow it.
>>
>> How are you testing this code? (next-dispatcher) is supposed to throw
>> an exception, but it will caught and used by the Web server when you
>> are using serve/servlet, etc.
>>
>> Jay
>>
>> On Tue, Dec 17, 2013 at 7:11 AM, Janos Tobias Locsei
>> <jtlocsei at cantab.net> wrote:
>> > I thought I'd add a note about what my overall objective with this is,
>> in
>> > case there's a completely different way of achieving the same thing.
>> >
>> > Basically what I want is to be able to serve a combination of apps and
>> > static html pages on my domain, but I don't want ".html" as the end of
>> the
>> > url for the static pages. So, if someone goes to the url
>> >
>> > http://mysite.com/lolcats
>> >
>> > ...then I'd like the web server will look in the directory
>> > /htdocs/static-html/ and check whether there's a file called
>> lolcats.html,
>> > and serve that page if it's there.
>> >
>> > My idea was that to achieve this I'd write a dispatch function that
>> would
>> > check the static-html directory for a file with the correct name, and
>> serve
>> > that page using the "include-template" function in web-server/templates.
>> >
>> > But if there's an easier/better way of achieving the same thing then I'm
>> > open to that.
>> >
>> > Tobias
>> >
>> >
>> >
>>
>>
>>
>> --
>> Jay McCarthy <jay at cs.byu.edu>
>> Assistant Professor / Brigham Young University
>> http://faculty.cs.byu.edu/~jay
>>
>> "The glory of God is Intelligence" - D&C 93
>>
>
>
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