On Fri, 2009-07-31 at 16:31 -0700, mviamari wrote:
> Hello,
>
> I'm trying to make a form for data entry into my database that uses
> ChoiceFields for foreign keys. Obviously, the ideal choice would be
> ModelChoiceField, however I'm not using the django ORM, so I've
> assumed that's not going to work (I'm using Elixir/SQLAlchemy).
>
> I originally set the choices parameter in the ChoiceField declaration
> to be derived from a query result from SQLAlchemy (returned as an
> array of tuples). The problem is that the choices don't update when
> the database changes. They are fixed to whatever was present when the
> server is initialized (or at least it appears to be).
If you have specified the choices field as a parameter to a Field
subclass in a Form class, then it will be evaluated whenever that Form
class is parsed (probably at import time). That's normal Python
behaviour.
> I'm looking for suggestions/advice on to get the ChoiceField choices
> to update when the form is the used.
"Used" is probably a bit ambiguous here. It's probably easier to think
in terms of "when an instance of the form class is created." The
solution is to update the choices attribute on the appropriate field in
the Form subclass's __init__() method. For example
class MyForm(forms.Form):
options = forms.ChoiceField()
def __init__(self, *args, **kwargs):
super(MyForm, self).__init__(*args, **kwargs)
choices = ... # <-- create a sequence of 2-tuples
self.fields["options"].choices = choices
You can do whatever you like to populate the "choices" variable in the
above fragment. The only requirement is that you end up with a sequence
of pairs which are the submitted form value and the human readable text
for the form element.
Regards,
Malcolm
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