Django NOT NULL约束失败

Question

我刚刚开始学习Django，我遇到了一个问题。 我有一个modelFormSet，用于为您创建的问题添加3个选项。 当我没有使用modelFormset并且只添加一个问题但是当我尝试迭代modelsFormset并将每个选项分配给刚刚创建的问题时，我没有问题我得到以下错误：

NOT NULL constraint failed: polls_choice.question_id

我认为这与question_id没有传递给选择模型有关，但我不确定如何解决它。 我已经运行了新的迁移，我认为我不能将空白或null设置为True，因为我需要选择和问题相关。 预先感谢您的帮助！

楷模

class Question(models.Model):
    question_text = models.CharField(max_length=200)
    pub_date = models.DateTimeField('date published')
    assigned_to = models.ManyToManyField(User)
    def __str__(self):
        return self.question_text
    def was_published_recently(self):
        now = timezone.now()
        return now - datetime.timedelta(days=1) <= self.pub_date <= now
    was_published_recently.admin_order_field = 'pub_date'
    was_published_recently.boolean = True
    was_published_recently.short_description = 'Published recently?'

class Choice(models.Model):
    question = models.ForeignKey(Question)
    choice_text = models.CharField(max_length=200)
    votes = models.IntegerField(default=0)
    def __str__(self):
        return self.choice_text

形式

class CreateQuestion(forms.ModelForm):
    class Meta:
        model = Question
        fields = ('question_text', 'assigned_to', 'pub_date',)


class AddChoices(forms.ModelForm):
    class Meta:
        model = Choice
        fields = ('choice_text',)

视图

def create_question(request):
    choices_formset = modelformset_factory(Choice, form=AddChoices, fields=('choice_text',), extra=3)
    if request.method == 'POST':
        question_form = CreateQuestion(data=request.POST)
        choice_form = choices_formset(request.POST, request.FILES)
        if question_form.is_valid and choice_form.is_valid:
            question = question_form.save()
            for choice in choice_form:
                choice.question = question
                choice.save()
            return HttpResponseRedirect(reverse('polls:index'))
        else:
            return render(request, 'polls/createquestion.html', {'question_form': question_form,
                                                                 'choice_form': choice_form, })
    else:
        question_form = CreateQuestion()
        choice_form = choices_formset(queryset=Choice.objects.none(),)
        return render(request, 'polls/createquestion.html', {'question_form': question_form,
                                                             'choice_form': choice_form, })

Answer 1

当您for choice in choice_form循环for choice in choice_form ，每个项目都是一个表单，因此设置question属性不起作用。

相反，您应该使用commit=False保存，设置问题，然后将对象保存到数据库。

for form in choice_form:
    choice = form.save(commit=False)
    choice.question = question
    choice.save()

Answer 2

问题在这里：

            for choice in choice_form:
                choice.question = question
                choice.save()

您在这里通过AddChoices表单进行迭代，而不是在Choice对象上进行迭代。 这意味着，您将问题保存为表单的属性，而不是模型实例的属性，并且不会传播到模型实例中。

要修复它，您可以尝试：

            for form in choice_form:
                choice = form.save(commit=False)
                choice.question = question
                choice.save()