On 17 Nov 2005, at 05:48, David Ascher wrote:
Goofy idea: use the Python logic to generate JS code to do
clientside validation based on the model-specified constraints.
Detailed specification and implementation are left as an exercise
to the reader. ;-)
Here's a concept for form validation with Ajax I've been knocking
around for ages that I would love to see in Django.
The most annoying thing about client-side validation is having to
duplicate the logic used in your server-side validation code.
Automating this is a nice idea but suffers from a couple of pretty
big problems:
1. Differences between JavaScript and Python regular expression syntax
2. Some checks, such as "is this user name already taken", can only
happen with server involvement
Here's how to fix both of these: have the client-side validation run
against the server-side validation logic using Ajax to communicate
between the two.
Say you have a form that submits to here:
/add-blog-entry/submit/
First, add another end point:
/add-blog-entry/validate/ (or validate_json or whatever)
Associate a pre-written (generic?) view with that end point that is
itself associated with a set of validation rules - in Django terms
that would probably be a manipulator of some sort. Every time a form
field is filled in the blur event causes JS to post the field name
and the data from that field at the validate endpoint. It returns a
simple JSON object representing if the data was valid, invalid or
undetermined (for fields which can't be validated without seeing
information from elsewhere in the form - we probably don't want to
send all form field data at once for every validation call as forms
involving big textareas can end up with a lot of data in them).
Invalid responses are accompanied by a JSON array of human readable
error messages.
JavaScript code on the client can then add green ticks or red crosses
to fields indicating valid and invalid data.
Cheers,
Simon
