[albatross-users] Handling user data error in forms

[Andrew McNamara]

>but this simple scheme doesn't seem to work very well with the navigation
>(I'm using server-based sessions).  It's not to bad for browser-based
>sessions, or simple apps with a single form on the front page, but breaks
>down if there are multiple forms in server-sessions.  (In particular, the
>browser "back" button doesn't necessarily go where the user might think it
>ought.)

The "back" key and server sessions really don't mix at all well. This
is one of the reasons I like the HiddenField sessions. 

One option we're considering is some complicated scheme involving
embedding version numbers and maintaining an LRU of "forked" sessions
(browsers with a "duplicate window" button cause related trouble).

You can often structure your application so it's a little more forgiving
of the occasional "back" (for example, making sure form controls are
unique, and using a common page_process function), but it's a hard
problem.

The RandomPage application class was one answer to this problem, but
causes grief of it's own (in particular, browsers flagging redirects on
form submission as a security risk).

-- 
Andrew McNamara, Senior Developer, Object Craft
http://www.object-craft.com.au/