How to load a dynamic saved dropdown during edit - ajax

Question

In my app, i have a chained dropdown in which i am getting the second dropdown via jquery ajax, which works well.So i am trying to edit this saved data and load it back to an edit form, but the dropdown is showing empty. This is what i have done so far
Here is my model.py
class SchoolFees(models.Model):
fid = models.ForeignKey(FacultyData, on_delete= models.SET_NULL, null=True)
did = models.ForeignKey(DepartmentData, on_delete= models.SET_NULL, null=True)
sid = models.ForeignKey(SessionData, on_delete= models.SET_NULL, null=True)
amount = models.CharField(max_length=30)
def __str__(self):
return self.amount
forms.py
class FeesCreationForm(forms.ModelForm):
fid = forms.ModelChoiceField(queryset=FacultyData.objects.all(), empty_label="--Select Faculty--",
widget=forms.Select(attrs={'class': 'form-control'}))
did = forms.ModelChoiceField(queryset=DepartmentData.objects.all(), empty_label="--Select Faculty First--",
widget=forms.Select(attrs={'class': 'form-control'}))
sid = forms.ModelChoiceField(queryset=SessionData.objects.all(), empty_label="--Select Session--",
widget=forms.Select(attrs={'class': 'form-control'}))
class Meta:
model = models.SchoolFees
fields = ['sid', 'fid', 'did', 'amount']
widgets = {
'amount': forms.TextInput(attrs={'class': 'form-control', 'placeholder': 'Enter Amount'})
}
def __init__(self, *args, **kwargs):
super(FeesCreationForm, self).__init__(*args, **kwargs)
self.fields['did'].queryset = DepartmentData.objects.none()
# Get did queryset for the selected fid
if 'fid' in self.data:
try:
fd = int(self.data.get('fid'))
self.fields['did'].queryset = DepartmentData.objects.filter(fid_id=fd).order_by('id')
except (ValueError, TypeError):
pass # invalid input from the client; ignore and use empty queryset
Here is my view.py
def edit_fee(request, pk):
app = settings.CONFIG
post = get_object_or_404(SchoolFees, pk=pk)
if request.method == 'POST':
form = FeesCreationForm(request.POST, instance=post)
if form.is_valid():
form.save()
messages.add_message(request, messages.WARNING, "Fees record updated successfully")
return redirect('bursary:create_fee')
else:
# bring edit form out
form = FeesCreationForm(instance=post)
table = FeesTable(SchoolFees.objects.all())
RequestConfig(request, paginate={'per_page': 10}).configure(table)
context = {"form": form, "fees": table, 'app': app}
return render(request, 'editfee.html', context)
I expect that the saved value is pass to the dropdown with other form fields which are already showing

Answer 1

After going through this post, i was able to solve it when reading the comments. All i needed was to add a backward relationship to my init function.
class FeesCreationForm(forms.ModelForm):
fid = forms.ModelChoiceField(queryset=FacultyData.objects.all(), empty_label="--Select Faculty--",
widget=forms.Select(attrs={'class': 'form-control'}))
did = forms.ModelChoiceField(queryset=DepartmentData.objects.all(), empty_label="--Select Faculty First--",
widget=forms.Select(attrs={'class': 'form-control'}))
sid = forms.ModelChoiceField(queryset=SessionData.objects.all(), empty_label="--Select Session--",
widget=forms.Select(attrs={'class': 'form-control'}))
class Meta:
model = models.SchoolFees
fields = ['sid', 'fid', 'did', 'amount']
widgets = {
'amount': forms.TextInput(attrs={'class': 'form-control', 'placeholder': 'Enter Amount'})
}
def __init__(self, *args, **kwargs):
super(FeesCreationForm, self).__init__(*args, **kwargs)
self.fields['did'].queryset = DepartmentData.objects.none()
# Get did queryset for the selected fid
if 'fid' in self.data:
try:
fd = int(self.data.get('fid'))
self.fields['did'].queryset = DepartmentData.objects.filter(fid_id=fd).order_by('id')
except (ValueError, TypeError):
pass # invalid input from the client; ignore and use empty queryset
elif self.instance.pk:
self.fields['did'].queryset = self.instance.fid.departmentdata_set.order_by('id')
#backward relation - for this faculty selected, check its deparm
#every department has its faculty
# #in other word, which dept has their foreign key pointing to the current instance of faculty