On Nov 30, 1:37 am, SaltyCow <jeff.bienkow...@gmail.com> wrote:
> For example, I have a table "quote" and I would like to be able to
> refer to a given quote as something like "Q100003". The actual primary
> key (id) of the row for that quote may be just plain "3", but it's not
> convenient to refer to a quote that way in emails, etc.
I had to do something similar recently: auto-create a "password"-like
key in a record (created as a sub-component of uuid.uuid4()), but only
on record creation. The problem with compute() is that it runs every
time a record is updated, and the dict passed to the compute()
function does not contain the current value of the field being
computed, so you can't monitor that for deciding whether or not to
create a new one.
OTOH, if you're always going to base your number on the PK, then the
PK will never change and therefore compute() should be fine, because
your compute function will always calculate the same output for a
given record.
Perhaps something like this:
Field('myfield', compute=lambda d: 'Q' + str(d['id'] + 10000))
(Post your code for your compute() function implementation)
In the end, for my scenario, we just wrote a custom validator. I
don't have the code handy right now, but the book description of
validators is reasonable, so that should be enough to get you started
if compute() is insufficient for your needs.
