revlet and path

[Devin Asay]

Hi Tereza,

On Aug 6, 2009, at 7:29 AM, Tereza Snyder wrote:
>
> It sounds like this means that I can't reliably reference files—like
> external stacks or configuration files—'next to' my revlet on the
> server. Is this true? How about the value of 'the directory' or
> 'default folder'? How about referenced images?
>
> I routinely store application resources in a folder, 'resources', next
> to my apps that contain all kinds of stuff. I compute paths at startup
> depending on the effective filename. Do I have to change my
> architecture?

This is no different than stacks launched from a web server using a  
desktop-based launcher app. The launched stack resides only in RAM so  
it has no filename value, as it was not launched from a stackfile in  
the local filesystem. If there is a defaultFolder, it's on the desktop  
file system. When you work in this environment, you just have to  
change your thinking a little bit. You can still have prefs and  
resource files in a folder next to your stack, but instead of looking  
in a relative filepath, you have to remember the URL to the stack  
(obviously you know it or you couldn't launch the stack.) Remove the  
stackname from the URL and you're left with the web URL ("filepath",  
if you will) to the folder containing the stack. Just build a new URL  
by appending the folder and file name of the resources/prefs file and  
call it that way.

For example, let's say my revlet is at:

   http://devin.com/revlets/mystackpage.html

It should be fairly simple to either derive the URL within the revlet  
stack or to pass the URL as a parameter when launching the revlet. (I  
haven't tried this myself yet, but I've seen others describe here how  
to pass params.) Once your revlet stack has that information, just  
have it do:

   set the itemdelimiter to "/"
   put item 1 to -2 of tURLreceivedAsParam & "/resources/myprefs.txt"  
into tPrefsURL
   put URL tPrefsURL into tMyPrefs
   -- now do whatever you want with the prefs.

Like I said, I use a model similar to this all the time with stacks  
launched from a web server, and it works great. I haven't explicitly  
tried it with a revlet, but I see no reason why it wouldn't work. Of  
course, one of the problems with this approach is that you can't write  
to that web-based resource file. Welcome to the Web!

You have to use other strategies, such as using a database server like  
MySQL or PostgreSQL, cookies, or an on-rev CGI that can write to the  
server file.

So it's definitely doable, you just have to adapt to the new, more  
restrictive Web environment.

Regards,

Devin

Devin Asay
Humanities Technology and Research Support Center
Brigham Young University