On Friday, December 5, 2014 4:21:20 AM UTC-5, Francisco Ribeiro wrote:
>
> Yes, Anthony you are right, there is no need to add more validators. I was
> just thinking of a different naming convention to clear the ambiguity we
> have now, because for checkboxes IS_NOT_EMPTY() means the same as
> IS_EQUAL_TO(True).
>
Slight correction -- it would actually be IS_EQUAL_TO('on'), as "on" is the
standard value given to checkbox input elements in SQLFORMs.
> Unfortunately, I don't think there is a way to achieve the behaviour I am
> looking for without adding some JavaScript on the client side when the form
> is generated in order to create a distinction between value not submitted
> (which is what the IS_NOT_EMPTY() would use) and False.
>
Yes, you could achieve the behavior you want with a special validator that
returns success whether it is fed "on" or None, but such a validator would
be pointless.
Keep in mind, though, that there is not actually any distinction to be made
on the client side -- "value not submitted" is literally the exact same
thing as False (i.e., when the checkbox is checked, the input element's
value is submitted, and when it is not checked, no value is submitted).
Of course, you could use Javascript to detect when the form is being
submitted, and in that case intercept the form submission, serialize the
form elements, and add the checkbox name with a value such as "off", which
would result in a value always being submitted for the checkbox (still,
though, there would be no distinction between "off" and value not
submitted). In that case, IS_NOT_EMPTY() would work as you would like it
to, but it would serve no purpose, as it would always generate a successful
validation. Much simpler just to remove the is_required attribute from
boolean fields.
Note, the issue is not with the IS_NOT_EMPTY validator, which works exactly
as it should. The issue is with the _validate method of the INPUT helper.
For checkbox inputs, it uses request.vars.get(name) to retrieve the value
of the checkbox element, and that returns None if the checkbox wasn't
checked (i.e., the checkbox variable is not in request.vars in that case).
If instead it used something like request.vars.get(name, 'off'), everything
would work as you expected (though SQLFORM.accepts would also have to be
changed to accommodate this). The problem with that approach is that the
INPUT element itself can be used outside of SQLFORMs, and there is no
obvious standard for an unchecked value, so the best approach is to remain
consistent with how the browser works and simply leave the value as missing
in case the box is not checked.
Anthony
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