Django模型继承

Question

我正在尝试在我的网站上修复rsvp系统。 我有链接到用户模型的联系人模型。 来宾模型链接到联系和事件模型。

class Contact(models.Model):
first_name = models.CharField(_("First name"), max_length=30, )
last_name = models.CharField(_("Last name"), max_length=30, )
user = models.ForeignKey(User, unique=True)
dob = models.DateField(_("Date of birth"), blank=True, null=True)
email = models.EmailField(_("Email"), blank=True, max_length=75)
notes = models.TextField(_("Notes"), max_length=500, blank=True)
create_date = models.DateField(_("Creation date"))

class Guest(models.Model):
event = models.ForeignKey(Event, related_name='guests')
contact = models.ForeignKey(Contact, related_name='guests')
attending_status = models.CharField(max_length=32, choices=ATTENDING_CHOICES, default='no_rsvp')
number_of_guests = models.SmallIntegerField(default=0)
comment = models.CharField(max_length=255, blank=True, default='')
updated = models.DateTimeField(blank=True, null=True)

def _get_email(self):
    return u'%s' % (self.contact.email)
email = property(_get_email)

....

我尝试在Guest模型的基础上修复RSVP表单：

class RSVPForm(forms.Form):
email = forms.EmailField()
name = forms.CharField(max_length=128)
attending = forms.ChoiceField(choices=VISIBLE_ATTENDING_CHOICES, initial='yes', widget=forms.RadioSelect)
number_of_guests = forms.IntegerField(initial=0)
comment = forms.CharField(max_length=255, required=False, widget=forms.Textarea)

def __init__(self, *args, **kwargs):
    if 'guest_class' in kwargs:
        self.guest_class = kwargs['guest_class']
        del(kwargs['guest_class'])
    else:
        self.guest_class = Guest
    super(RSVPForm, self).__init__(*args, **kwargs)

def clean_email(self):
    try:
        guest = self.guest_class.objects.get(email=self.cleaned_data['email'])
    except ObjectDoesNotExist:
        raise forms.ValidationError, 'That e-mail is not on the guest list.'

    if hasattr(guest, 'attending_status') and guest.attending_status != 'no_rsvp':
        raise forms.ValidationError, 'You have already provided RSVP information.'

    return self.cleaned_data['email']

def clean_number_of_guests(self):
    if self.cleaned_data['number_of_guests'] < 0:
        raise forms.ValidationError, "The number of guests you're bringing can not be negative."
    return self.cleaned_data['number_of_guests']

def save(self):
    guest = self.guest_class.objects.get(email=self.cleaned_data['email'])

    if self.cleaned_data['name']:
        guest.name = self.cleaned_data['name']

    guest.attending_status = self.cleaned_data['attending']
    guest.number_of_guests = self.cleaned_data['number_of_guests']
    guest.comment = self.cleaned_data['comment']
    guest.save()
    return guest

该表格由以下视图处理：

@login_required
def event_view(request, slug, model_class=Event, form_class=RSVPForm,    template_name='rsvp/event_view.html'):
event = get_object_or_404(model_class, slug=slug)

if request.POST:
    form = form_class(request.POST)

    if form.is_valid():
        guest = form.save()
        return HttpResponseRedirect(reverse('rsvp_event_thanks', kwargs={'slug': slug, 'guest_id': guest.id}))
else:
    form = form_class()

return render_to_response(template_name, {
        'event': event,
        'form': form,
        }, context_instance=RequestContext(request))

提交表单后，出现以下错误：

“无法将关键字'email'解析为字段。选择包括：Attinging_status，评论，联系人，事件，ID，number_of_guests，更新”

经过数小时的网络搜索，当我使用Guest.email并从Contact.email呈现其价值时，我仍然不知道为什么我只是在选择列表中有“联系人”。

Answer 1

您模型中的访客没有字段电子邮件。 它在您的联系人模型上。

您没有提到哪条线触发了您的错误，但是我想这可能是其中之一：

guest = self.guest_class.objects.get(email=self.cleaned_data['email'])

如果您要搜索与给定电子邮件地址的联系人链接的来宾，则需要将其更改为使用contact__email以便它将为您进行加入：

guest = self.guest_class.objects.get(contact__email=self.cleaned_data['email'])

问题的根源也许是在您的模型之间存在继承关系，而我根本看不到这种关系。 您有一个简单的ForeignKey关系，该关系应该对您有用，只是不要将其与继承混淆，在这种情况下，您将设置Guest以通过子类继承来继承Contact的属性。

Answer 2

因为django的ORM在SQL级别上工作。 表/模型中没有“电子邮件”列（或定义的字段），只有python属性。 Django不知道需要对其他表进行JOIN操作。

相反，只需使用Django的__ JOIN /字段查找语法即可：

guest = self.guest_class.objects.get(contact__email=self.cleaned_data['email'])

http://docs.djangoproject.com/en/dev/topics/db/queries/#lookups-that-span-relationships