[racket] formlets and validation

2011/3/29 Eric Tanter <etanter at dcc.uchile.cl>:
> Hi,
>
> I'm exploring formlets (enjoying them for the most part!), and I'm wondering what is the best way to handle input validation. Following the tutorial/guide on formlets results in the web app throwing exceptions whenever formlet-process encounters improper bindings.
> (eg. self-contract violation: expected <integer?>, given: #f
>  contract on input-int from ...)
>
> However, those are not really helpful for the user.
> I'm wondering:
> a- is there a way to specify some validation to be done on the client side?

No. I think it would be nice to do a little DSL that does that, but I have not.

> if not:
> b- is there a best practice to expose users to their malformed input in a precise manner? (ie. which input field was incorrectly filled)

I've played with a maybe-formlet that catches exceptions in the
processing step of its argument and then coded in the behavior of the
result page to show the problems. I haven't found an API that I really
like.

This would be a good place to improve in the Web Server. I plan on
doing it as I need to in my apps, but I'd love to see what ideas, etc
others have. I'm happy too to take something useful that others make
and improve and support it.

Jay

>
> Thanks!
>
> -- Éric
>
>
>
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-- 
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