How to save many to many relationship? - django

Question

I'm almost using following code(I striped down a little bit), I use auto complete light to load users and users can insert different people name(users) seperated by comma. the problem is when I try to save I get following error
ValueError at /write/
"<Article: test1>" needs to have a value for field "article" before this many-to-many relationship can be used.
models.py
class Article(models.Model):
author = models.ForeignKey(User,)
people = models.ManyToManyField(User, related_name="with", null=True,)
content = models.TextField()
forms.py
class ArticleForm(forms.ModelForm):
people = forms.CharField(widget=autocomplete_light.TextWidget('UserAutocomplete'))
class Meta:
model = Article
views.py
def write(request):
if request.POST:
form = ArticleForm(request.POST)
if form.is_valid():
content = form.cleaned_data['content']
user = User.objects.get(username=request.user.username)
people_str = form.cleaned_data['accompanied']
people = [x.strip() for x in accompanied_str.split(',')]
article = Article(
content = content,
author = user,
)
for username in accompanied:
user = User.objects.get(username=username)
article.people.add(user)
article.save()
return HttpResponseRedirect('/success/')

Answer 1

In order to create a relation you need the ids of both side. The newly created article has no id yet. If you save the article first and then add people to it it should work fine.
article = Article(
content = content,
author = user,
)
article.save()
article.add(*User.objects.filter(username__in=accompanied))
The process of adding people can be cheaper by getting all users that have a username from the list of accompanied in one fetch.