Try
IS_IN_DB(..., multiple=(0, 3))
The "multiple" argument to IS_IN_SET and IS_IN_DB can be a list or tuple
specifying a minimum and maximum number of items to be selected (strictly
less than on the max, so set the max to 3 to make sure there are no more
than 2).
Anthony
On Wednesday, December 14, 2011 11:19:40 PM UTC-5, ニコノコ wrote:
>
> I have a list:reference field and would like a user to select none or up
> to two values from the list
>
> I could validate by calling onvalidation but I'm wondering if there's any
> built-in validator that should work? I've tried the following, none of
> which worked for me:
>
> - IS_LENGTH(minsize=0,maxsize=2)
> - IS_EXPR('len(value)<=2')
>
>
>
>
