Django restrict foreign key options - django

Question

So I have three models:
class Session(models.Model):
id = models.UUIDField('ID', default=uuid.uuid4, primary_key=True, editable=False)
start_time = models.TimeField('Start Time', default=None)
end_time = models.TimeField('End Time', default=None)
def __str__(self):
return "{}-{}".format(str(self.start_time), str(self.end_time))
class Slot(models.Model):
id = models.UUIDField('ID', default=uuid.uuid4, primary_key=True, editable=False)
timings = models.ForeignKey('Session', on_delete=models.DO_NOTHING, related_name='slot_timings')
available_counsellors = models.ManyToManyField(User, limit_choices_to={'role': 'COUNSELLOR'}, related_name='available_counsellors')
def __str__(self):
return str(self.timings)
class ChatSession(models.Model):
def get_access_code():
while True:
access_code = get_random_string(length=6, allowed_chars=('ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789'))
if not ChatSession.objects.filter(access_code=access_code).exists():
return access_code
id = models.UUIDField('ID', default=uuid.uuid4, primary_key=True, editable=False)
client = models.ForeignKey(User, limit_choices_to={'role': 'CLIENT'}, on_delete=models.DO_NOTHING, related_name='client_user')
counsellor = models.ForeignKey(User, limit_choices_to={'role': 'COUNSELLOR'}, on_delete=models.DO_NOTHING, related_name='counsellor_user')
access_code = models.CharField('Access Code', default=get_access_code, max_length=6)
topic = models.CharField('Topic', default=None, blank=True, null=True, max_length=255)
slot = models.ForeignKey(Slot, on_delete=models.DO_NOTHING, default=None)
def __str__(self):
return str(self.topic)
In the chat session model, I want to limit the options for counsellor field to the available_counsellors list in slot model.
How can I do this??
I want the same to reflect in my admin view also.

Answer 1

You need to update the queryset on the counsellor form field.
Assuming you are using a ModelForm, you can do this in your view:
chat_session = ChatSession.objects.get(pk=1)
form = ChatSessionForm(instance=chat_session)
form.fields["counsellor"].queryset = chat_session.slot.available_counsellors
You can alternatively do it in your ModelForm:
class ChatSessionForm(forms.ModelForm):
def __init__(self, *args, **kwargs):
super (ChatSessionForm, self).__init__(*args, **kwargs)
if self.instance and self.instance.slot:
options = self.instance.slot.available_counsellors
else
options = User.objects.none()
self.fields['counsellor'].queryset = options
For Django admin, something like this should work:
class ChatSessionAdmin(admin.ModelAdmin):
def render_change_form(self, request, context, *args, **kwargs):
if kwargs['obj'].slot:
options = kwargs['obj'].slot.available_counsellors
else:
options = User.objects.none()
context['adminform'].form.fields['counsellor'].queryset = options
return super(ChatSessionAdmin, self).render_change_form(request, context, args, kwargs)