Django: When form is submitted, auto-fill a field - django

Question

I'm looking to auto-fill a field when I submit a form so it is identical to another field.
I have a createView with a modelForm. The idea is the user writes his/hers name, which then when submitted fills out the display_name field as well. I know it's weird "why have two of the same", but it has a purpose.
Here's my code - I'm guessing I need to create a context that gets the display_name and sets it to be equal to the name?
views.py
class CreateIdentity(CreateView):
template_name = 'admin/CreateIdentity.html'
model = Identity
form_class = CreateIdentityForm
queryset = Identity.objects.all()
def get_context_data(self, **kwargs):
context = super(CreateIdentity, self).get_context_data(**kwargs)
context["user_id"] = User.objects.get(username=self.request.user)
return context
def form_valid(self, form):
form.instance.user_id = self.request.user
return super().form_valid(form)
def get_success_url(self):
return reverse_lazy("view_identity_created_with_slug", kwargs={'slug': self.object.slug})
models.py
class Identity(models.Model):
name = models.CharField(max_length=200, null=False)
display_name = models.CharField(max_length=200)
slug = models.SlugField(max_length=100)
user_id = models.ForeignKey(User, db_column="username", on_delete=models.CASCADE, null=False)
forms.py
class CreateIdentityForm(forms.ModelForm):
name = forms.CharField(required=True, widget=forms.TextInput(attrs={
'spellcheck': "false",
"class": "identity_name_input",
'placeholder': "Write your identity"}),
)
class Meta:
model = Identity
fields = ["name"]
def __str__(self):
return self.name

Answer 1

In the .form_valid(…) [Django-doc], you can specify the display_name based on the cleaned data of the form:
class CreateIdentity(CreateView):
template_name = 'admin/CreateIdentity.html'
model = Identity
form_class = CreateIdentityForm
queryset = Identity.objects.all()
def get_context_data(self, **kwargs):
context = super(CreateIdentity, self).get_context_data(**kwargs)
context["user_id"] = User.objects.get(username=self.request.user)
return context
def form_valid(self, form):
form.instance.user_id = self.request.user
form.instance.display_name = form.cleaned_data['name']
return super().form_valid(form)
def get_success_url(self):
return reverse_lazy("view_identity_created_with_slug", kwargs={'slug': self.object.slug})