NOT NULL 约束失败：尝试保存表单集答案

【问题标题】：NOT NULL constraint failed: Trying to save formsetNOT NULL 约束失败：尝试保存表单集
【发布时间】：2016-04-20 12:48:23
【问题描述】：

注意：Django/Python 初学者，希望这个问题清楚。

我正在创建一个表单，可以在一个表单中一次编辑模型（来宾）的多个实例，并同时提交。

此 Guest 模型链接到父模型 Invite，这意味着多个 Guest 附加到单个 Invite。

我已经设法为每个访客创建了一个表单集并显示它，但是当我提交它时，我收到以下错误。

NOT NULL constraint failed: app_guest.invite_id

我假设这是因为它没有将数据保存到的邀请，但我不知道把它要求的 invite_id 放在哪里。

到目前为止，这是我的观点：

def extra_view(request, code):
    # Get the specific invite
    invite = get_invite(code)

    # Get guests attached to this invite
    guests = invite.guest_set.all()

    # Get the context from the request.
    context = RequestContext(request)

    # Store object of guests marked as attending
    guests_attending = invite.guest_set.filter(attending=True, invite=invite)

    form = ExtraForm(data=request.POST or None)

    if form.is_valid():
        # Save the new category to the database.
        ### FAILS HERE
        form.save(commit=True)

        # Go to Confirm page
        HttpResponseRedirect('confirm')
    else:
        # The supplied form contained errors - just print them to the terminal for now
        print form.errors

    if guests_attending.count() > 1:
        # If the request was not a POST, display the form to enter details.
        guest_formset = modelformset_factory(Guest, form=ExtraForm, extra=0, max_num=guests_attending.count())

        # Filter the formset so that only guests marked as attending are
        filtered_guest_form = guest_formset(queryset=guests.filter(attending=True))

        # Return the view
        return render_to_response('weddingapp/extra.html', {'GuestForm': filtered_guest_form, 'invite': invite, 'guests_attending': guests_attending, 'form_errors': form.errors}, context)

    else:
        # Since there's no guests to create a form for, return Confirm view
        return render(request, 'weddingapp/confirm.html', {
            'invite': invite,
        })

这是我的访客模型：

@python_2_unicode_compatible
class Guest(models.Model):
    invite = models.ForeignKey(Invite, on_delete=models.CASCADE)
    guest_name = models.CharField(max_length=200)
    diet = models.CharField(max_length=250)
    transport = models.NullBooleanField(default=False, null=True)
    attending = models.NullBooleanField(null=True)

    def __str__(self):
        return self.guest_name

这是表格：

class ExtraForm(forms.ModelForm):
    diet = forms.CharField(max_length=128, help_text="Please enter your diet restrictions", required=False)
    transport = forms.BooleanField(initial=False, help_text="Will you be needing transport?", required=False)

    # An inline class to provide additional information on the form.
    class Meta:
        # Provide an association between the ModelForm and a model
        model = Guest
        fields = ('diet', 'transport')

任何帮助将不胜感激。即使是关于构建所有这些的更好方法的建议也会有所帮助。谢谢。

【问题讨论】：

标签： python django formset

【解决方案1】：

您的表单不包含invite 字段，因此您必须在保存到数据库之前对其进行设置。

if form.is_valid():
    # Save the new category to the database.
    instance = form.save(commit=False)
    instance.invite = invite
    instance.save()  # save to the db, now that we have set the invite
    ...

【讨论】：