django Initialising Choices in Form from Class Based View - django

Question

I've seen a lot of answers about how this is solved when not using Class Based Views. Is there some really obvious thing I'm missing about doing it with CBVs?
Basically I want to have a MultipleChoiceField in my form which has choices determined by what is happening in the view. e.g. I use the PK from the URL to do some backend requests and then those should be used to populate the choices.
# forms.py
from django.forms import Form, MultipleChoiceField, CharField
class EmailForm(Form):
users = MultipleChoiceField(required=False)
subject = CharField(max_length=100)
message = CharField()
def __init__(self, users=None, *args, **kwargs):
super(EmailForm, self).__init__(*args, **kwargs)
if users:
self.fields['users'].choices = users
#urls.py
from django.conf.urls import url, patterns
from .views import EmailView
# url patterns
urlpatterns = patterns('',
url( r'^(?P<pk>\d+)$', EmailView.as_view(), name="maindex" ),
)
#views.py
from django.views.generic import FormView, TemplateView
from .forms import EmailForm
class EmailView(FormView):
template_name = 'myapp/email.html'
form_class = EmailForm
success_ulr = '/thanks/'
def form_valid(self, form):
# Do stuff here
return super(EmailView, self).form_valid(form)
Basically it boils down to how/where to call the init function from the view. How do I do that? Or is there another way I've missed? I thought of overriding get_form_kwargs in the view, but couldn't make that do anything.
Thanks

Answer 1

The view:
from django.views.generic import FormView
class EmailView(FormView):
# ...
def get_form_kwargs(self):
kwargs = super(EmailView, self).get_form_kwargs()
# get users, note: you can access request using: self.request
kwargs['users'] = users
return kwargs
The form:
from django import forms import Form
class EmailForm(Form):
users = MultipleChoiceField(required=False)
# ...
def __init__(self, *args, **kwargs):
self.users = kwargs.pop('users', None)
super(EmailForm, self).__init__(*args, **kwargs)
self.fields['users'].choices = self.users

Answer 2

Basically, what I've done in a similar case is the following (Python 3.5, Django 1.8):
def get_form(self, *args, **kwargs):
form= super().get_form(*args, **kwargs)
form.fields['rank'].choices= <sequence of 2-tuples>
return form
where obviously rank is the field name. This way I use the default form.

Answer 3

Alright, the FormMixin calls get_form to get the form-class which looks like
def get_form(self, form_class):
"""
Returns an instance of the form to be used in this view.
"""
return form_class(**self.get_form_kwargs())
So you can either override get_form to instance your Form yourself
def get_form(self, form_class):
return EmailForm(files=self.request.FILES or None,
data=self.request.POST or None,
users=some_user_queryset)
or stay a bit more generic and override get_form_kwargs to something like
def get_form_kwargs(self):
form_kws = super(EmailView, self).get_form_kwargs()
form_kws["users"] = some_user_queryset
return form_kws

Answer 4

One way to do it is:
class EmailView(FormView):
# ...
def get(self, request, *args, **kwargs):
self.users = ...
return super(EmailView, self).get(request, *args, **kwargs)
def get_form_kwargs(self):
kwargs = super(EmailView, self).get_form_kwargs()
kwargs['users'] = self.users
return kwargs
This allows you to set the user choices in the view and to pass them to the form.

Answer 5

You can override get_form.
I needed to update the choices for ChoiceField based on logged in user.
Form:
class InteractionCreateForm(forms.Form):
device = forms.ChoiceField(choices=[(None, '----------')])
...
View:
class InteractionCreateView(FormView):
form_class = InteractionCreateForm
...
def get_form(self, form_class=None):
form_class = super().get_form(form_class=None)
form_class.fields['device'].choices = \
form_class.fields['device'].choices \
+ [(device.pk, device) for device in Device.objects.filter(owner=self.request.user.id)]
return form_class