Instantiate a modelForms MultiSelectCheckBox widget - django

Question

I am using ModelForms with a ModelMultipleChoiceField widget. I have 2 questions:
My checkbox widget for Treatment Options from SelectOptionForStateForm renders existing selections from the stateoption table in my database. How does it know to look in that table for existing records? In my views.py I am only passing the disease and state objects which do not look at the stateoption table.
How do I instantiate my SelectOutcomeForOptionForm so that my Treatment Outcomes checkbox is also pre-selected from the stateoptionoutcome table in my database?
forms.py
class SelectOptionForStateForm(forms.ModelForm):
class Meta:
model = State
exclude = ['state', 'relevantdisease']
def __init__(self, *args, **kwargs):
disease=kwargs.pop('disease', None)
super(SelectOptionForStateForm, self).__init__(*args, **kwargs)
self.fields['relevantoption']=forms.ModelMultipleChoiceField(queryset=Option.objects.filter(relevantdisease_id=disease),required=True, widget=forms.CheckboxSelectMultiple)
self.fields['relevantoption'].label="Treatment Options"
class SelectOutcomeForOptionForm(forms.ModelForm):
class Meta:
model = StateOption
exclude = ['partstate', 'partoption']
def __init__(self, *args, **kwargs):
disease=kwargs.pop('disease', None)
super(SelectOutcomeForOptionForm, self).__init__(*args, **kwargs)
self.fields['relevantoutcome']=forms.ModelMultipleChoiceField(queryset=Outcome.objects.filter(relevantdisease_id=disease),required=True, widget=forms.CheckboxSelectMultiple)
self.fields['relevantoutcome'].label="Treatment Outcomes"
views.py
def stateoptionoutcome(request, disease_id, state_id):
state = get_object_or_404(State, pk=state_id)
disease = get_object_or_404(Disease, pk=disease_id)
if request.method == "POST":
optionForm = SelectOptionForStateForm(request.POST, disease=disease, instance=state)
outcomeForm = SelectOutcomeForOptionForm(request.POST, disease=disease, instance=state)
if optionForm.is_valid() and outcomeForm.is_valid():
#Deletes state objects so there are no duplicate options in the database
try:
state_option = StateOption.objects.filter(partstate=state).delete()
except StateOption.DoesNotExist:
state_option = None
#Saves user options to database
for option_id in request.POST.getlist('relevantoption'):
state_option = StateOption.objects.create(partstate=state, partoption_id=int(option_id))
#Deletes stateoption objects found in StateOptionOutcome
try:
state_option_outcome = StateOptionOutcome.objects.filter(stateoption=state_option).delete()
except StateOptionOutcome.DoesNotExist:
state_option_outcome = None
#Saves user outcomes to database
for outcome_id in request.POST.getlist('relevantoutcome'):
state_option_outcome = StateOptionOutcome.objects.create(stateoption=state_option, relevantoutcome_id=int(outcome_id))
return HttpResponseRedirect(reverse('diseasestateoptionlist', kwargs={'disease_id':disease_id, 'state_id':state_id}))
models.py
class State(models.Model):
state = models.CharField(max_length=255)
relevantdisease = models.ForeignKey(Disease)
relevantoption = models.ManyToManyField(Option, through='StateOption')
class StateOption(models.Model):
partstate = models.ForeignKey(State)
partoption = models.ForeignKey(Option)
relevantoutcome = models.ManyToManyField(Outcome, through='StateOptionOutcome')
class StateOptionOutcome(models.Model):
stateoption = models.ForeignKey(StateOption)
relevantoutcome = models.ForeignKey(Outcome)
outcomevalue = models.CharField(max_length=20)

Answer 1

I was able to solve #2 using this:
stateoptionlist = StateOption.objects.filter(partstate_id=state_id)
if not stateoptionlist:
stateoption = state
else:
stateoption = stateoptionlist[0]
I pass the state instance if the stateoptionlist returns an empty list (ie, there are no records in the StateOption table). Updating the views.py, for every SelectOutcomeForOptionForm, my instance is replaced with stateoption.
I'm interested to see if there's a more efficient way of solving #2.