Django模型继承

Question

我试图修复我的网站上的rsvp系统。我有与用户模型链接的联系人模型。访客模型与联系人和事件模型相关联。

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) 

.... 

我尝试修复旅客模型的基础上RSVP形式：

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 

这种形式由下面的视图处理：

@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，我出现以下错误：

“无法将关键字'电子邮件'解析为字段。可以选择：attending_status，评论，联系，事件，身份证，number_of_guests，更新“

经过几个小时的搜索网络，我仍然无法弄清楚为什么我在选择列表中只是”联系“，而我正在使用Guest.email从Contact.email呈现其值。

Answer 1

您的模型中的来宾没有字段电子邮件。它在您的联系人模型上。

你没有提到这行触发你的错误，但我猜这将是其中之一：

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

如果您正在搜索链接到的联系人与给定客人电子邮件，你会想改变它使用contact__email所以它会做的加入为你：

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

你的问题的根源也许是认为你有你的模型之间的继承关系，我没有看到一个。你有一个简单的ForeignKey关系，它应该适用于你，只是不要将它与继承混淆起来，在这里你将建立一个Guest来通过子类继承Contact的属性。

Answer 2

因为django的ORM在SQL级别上工作。在你的表/模型中没有'email'列（或定义的字段），只有一个python属性。 Django不知道它需要加入到其他表中。

所以，应该使用Django的__ JOIN /场查找语法：

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