Set form field value before is_valid() - django

Question

I'm having a bit of trouble grasping how to do this. I've put my best effort into searching Google without any luck.
I'll start with a bit of code and explain what I'm trying to do as I go:
models.py
class Action(models.Model):
title = models.CharField(max_length=200)
owner = models.ForeignKey(User, related_name='actions')
created_by = models.ForeignKey(User, related_name='+', editable=False)
modified_by = models.ForeignKey(User, related_name='+', editable=False)
class ActionForm(ModelForm):
class Meta:
model = Action
views.py
By default, there is a dropdown field for owner. I have an icon that allows the user to enter a new username in a text field instead for owner. I check to see if owner_new was submitted and if so, create that user. I then need to set the owner field to that value so that form.is_valid() will be true.
def action_create(request):
if request.method == 'POST':
form = ActionForm(request.POST)
# check if new user should be created
if 'owner_new' in request.POST:
# check if user already exists
user = User.objects.get(username=request.POST.get('owner_new'))
if not user:
user = User.objects.create_user(request.POST.get('owner_new'))
# HERE IS WHERE I'M STUMPED
form.owner = user.id
if form.is_valid(): # THIS FAILS BECAUSE form.owner ISN'T SET
action = form.save(commit=False)
action.created_by = request.user
action.modified_by = request.user
action.save()
return redirect('action_register:index')
else:
form = ActionForm()
return render(request, 'actions/create.html', {'form': form})

Answer 1

You can try this:
def action_create(request):
if request.method == 'POST':
form = ActionForm(request.POST)
# check if new user should be created
if 'owner_new' in request.POST:
# check if user already exists
user, _ = User.objects.get_or_create(username=request.POST.get('owner_new'))
updated_data = request.POST.copy()
updated_data.update({'owner': user})
form = MyForm(data=updated_data)
if form.is_valid(): # THIS FAILS BECAUSE form.owner ISN'T SET
action = form.save(commit=False)
action.created_by = request.user
action.modified_by = request.user
action.save()
return redirect('action_register:index')
else:
form = ActionForm()
return render(request, 'actions/create.html', {'form': form})
A cleaner way of doing this is:
add required=False to the owner field.
Now,
if form.is_valid(): # THIS DOES NOT FAIL EVEN IF form.owner ISN'T SET
action = form.save(commit=False)
if 'owner_new' in request.POST:
user, _ = User.objects.get_or_create(username=request.POST.get('owner_new'))
action.owner = user
action.created_by = request.user
action.modified_by = request.user
action.save()
return redirect('action_register:index')

Answer 2

I came into a similar situation and couldn't figure out how to do it the way I wanted. What I ended up with was putting a link to a UserForm which allows a user to create a new owner, and then redirect back to the ActionForm with the argument initial={owner: new_owner} included when instantiating the form.