Clash Royale CLAN TAG#URR8PPP

Django create new instances of a different model using the submitted form data of a model

I have a Topic model which has a ManyToManyField to the Tag model.
Similarly to stack overflow where you can submit new tags at the time of asking a question. I want to be able to create new tags when you create a topic.

A hacky solution from the top of my head.

Class TopicCreateView(CreateView):
model = Topic
template_name = 'blah'
fields = [
'blah'
]

def form_valid(self, form):
tags = self.request.POST.getlist(tags)
for tag in tags:
if not Tag.objects.filter(tag_string__iexact=tag):
try:
new_tag = Tag.objects.create(tag_string=tag)
except IntegrityError:
# stuff
return super().form_valid(form)


I'm new to Django and web frameworks in general, but this seems really hacky to me (if it even works). Given what I've read so far regarding FormSets and such, is there not a better way to achieve this?

2 Answers
2

Since the model code is not provided, I'm just guessing what you are thinking about:

def form_valid(self, form):
tags = self.request.POST.getlist('tags')
existed_tags = Tag.objects
.filter(tag_string__iexact=tags)
.values_list('tag_string', flat=True)
new_tags = set(tags) - set(existed_tags)

for tag in new_tags:
Tag.objects.create(tag_string=tag)
return super().form_valid(form)


Perhaps your original codes can work but just need improvement (and thus I don't think it was 'hacky'). You put the Tag QuerySet within a for loop so the database will be hit in each time of iteration. To get all of the tag values from db first then compare the difference and do further work may be a better way.

Tag

Moreover, I think tag creation should not put in form_valid since this is a 'model procedure'. To override the save() method of Topic model or using Signal may be a better choice. Yet this is just my preference and you can still keep this unchanged.

form_valid

save()

Topic

Topic.save()

CreateView

model=Topic

save()

Topic

I came up with a more acceptable solution keeping the model creation out of the View() and in the Form(), as defining form_class is still possible with the CreateView().

I took inspiration from how stack overflow handles tags, in that they accept a string and split each tag on '+'.

View()

Form()

form_class

CreateView()

'+'

There may be a way to further improve this but FormSets did not seem like viable option in this instance.

FormSets

Class TopicCreateForm(forms.ModelForm)
submitted_tags = forms.CharField(max_length=256)
class Meta:
model = Blah
fields = ['blah']

def clean_submitted_tags(self):
tags = self.cleaned_data.get(
'submitted_tags').split("+")

# validation here

return tags

def save(self, *args, **kwargs):
# get author from form instance
author = self.instance.author

tags = self.cleaned_data['submitted_tags']
existing_tags = Tag.objects.values_list(
'tag_string', flat=True)

for tag in [t for t in tags if t not in existing_tags]:
new_tag = Tag.objects.create(
tag_string=tag,
created_by=author)

new_tags = Tag.objects.filter(tag_string__in=tags)
new_tag_uuids = [t.pk for t in new_tags]

self.cleaned_data['tags'] = new_tag_uuids

return super().save(*args, **kwargs)


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