That’s correct. I am using a class variable since there doesn’t seem to be a
DRY - or at least not messy - way of manipulating this from __init__.
That said, your explanation makes sense and does answer the “why” of this. If
there’s a way of defining forms inside __init__ I haven’t found it… which is
not to say that it doesn’t exist.
Here’s an example of what I’m referring to:
(Pardon my poorly labeled model/form names)
```
class M2MForm(forms.ModelForm):
“”” Populate/update M2MModel name and m2m references ””"
REF_OPTIONS = ((r.id, r.name) for r in RefModel.objects.all())
ref_models = forms.MultipleChoiceField(
widget=forms.SelectMultiple,
choices=REF_OPTIONS,
required=False
)
class Meta:
model = M2MModel
fields = ['name']
```
> On Dec 22, 2020, at 9:31 AM, Carles Pina i Estany <car...@pina.cat> wrote:
>
>
>
> Hi,
>
> On Dec/22/2020, Benny M wrote:
>
>> I’ve ran into some unexpected behavior while testing a ModelForm with
>> a MultipleChoiceField and am trying to determine if this is a bug, or
>> if maybe I’m doing something out of the ordinary.
>
> I think that I might guess what it is. If I could see the code it might
> be easier.
>
> Are you doing something like:
>
> class SomeForm(forms.ModelForm):
> some_field_options = a_dynamic_expression_that_queries_the_DB
>
> def __init__(*args, **kwargs):
> your code
>
> So using a class variable instead of an instance variable?
>
> Class variables are initialised on "startup" (I'm simplifying) and only
> once (and might be used via __new__ on ModelFormMetaclass probably, read
> and validated).
>
> Either way, if it's not what I've guessed and you paste some code it
> might help me / someone else to understand it better.
>
> I had once a bug because of using datetime.now() in a class variable
> when I wanted it the "now" that the view was used not the "now" when the
> application was started up.
>
> --
> Carles Pina i Estany
> https://carles.pina.cat
>
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