在 Django 中保存表单数据之前的重复检查

Question

我得到了如下表格：

class CourseAddForm(forms.ModelForm):
  """Add a new course"""
  name = forms.CharField(label=_("Course Name"), max_length=100)
  description = forms.Textarea()
  course_no = forms.CharField(label=_("course Number"), max_length=15)


  #Attach a form helper to this class
  helper = FormHelper()
  helper.form_id = "addcourse"
  helper.form_class = "course"

  #Add in a submit and reset button
  submit = Submit("Add", "Add New Record")
  helper.add_input(submit)
  reset = Reset("Reset", "Reset")
  helper.add_input(reset)

def clean(self):
  """ 
  Override the default clean method to check whether this course has been already inputted.
  """    
  cleaned_data = self.cleaned_data
  name = cleaned_data.get('name')
  hic = cleaned_data.get('course_no')

  try:
    course=Course.objects.get(name=name)
  except Course.DoesNotExist:
    course=None

  if course:
    msg = u"Course name: %s has already exist." % name
    self._errors['name'] = self.error_class([msg])
    del cleaned_data['name']
    return cleaned_data
  else:
    return self.cleaned_data

  class Meta:
    model = Course

如您所见，当用户尝试添加该课程时，我重写了 clean 方法以检查该课程是否已存在于数据库中。这对我来说很好用。

但是，当我想为表单添加相同的检查以进行编辑时，问题发生了。因为是编辑，所以DB中已经存在相同课程名称的记录。因此，同样的检查会抛出错误课程名称已经存在。但我需要检查重复，以避免用户将课程名称更新为另一个已经存在的课程名称。

我正在考虑检查课程名称的值以查看它是否已更改。如果它已更改，则我可以进行与上述相同的检查。如果它没有改变，我不需要做检查。但我不知道如何获取原始数据进行编辑。

有谁知道如何在 Django 中做到这一点？

我的观点如下：

@login_required
@csrf_protect
@never_cache
@custom_permission_required('records.change_course', 'course')
def edit_course(request,course_id):
  # See if the family exists:
try:
  course = Course.objects.get(id=course_id)
except Course.DoesNotExist:
  course = None

if course:
  if request.method == 'GET':
    form = CourseEditForm(instance=course)
    return render_to_response('records/add.html',
                            {'form': form},
                            context_instance=RequestContext(request)
                            )
  elif request.method == 'POST':
    form = CourseEditForm(request.POST, instance=course)
    if form.is_valid():
      form.save()
      return HttpResponseRedirect('/records/')
    # form is not valid: 
    else:
      error_message = "Please correct all values marked in red."
      return render_to_response('records/edit.html', 
                              {'form': form, 'error_message': error_message},
                              context_instance=RequestContext(request)
                              )      
else:
  error = "Course %s does not exist. Press the 'BACK' button on your browser." % (course)
  return HttpResponseRedirect(reverse('DigitalRecords.views.error', args=(error,)))

谢谢你。

Answer 1

我认为您应该unique=True在Course.name现场设置并让框架为您处理该验证。

更新：

由于unique=True不是您的案例的正确答案，您可以通过以下方式检查：

def clean(self):
    """ 
    Override the default clean method to check whether this course has
    been already inputted.
    """    
    cleaned_data = self.cleaned_data
    name = cleaned_data.get('name')

    matching_courses = Course.objects.filter(name=name)
    if self.instance:
        matching_courses = matching_courses.exclude(pk=self.instance.pk)
    if matching_courses.exists():
        msg = u"Course name: %s has already exist." % name
        raise ValidationError(msg)
    else:
        return self.cleaned_data

class Meta:
    model = Course

作为旁注，我还更改了您的自定义错误处理以使用更标准的ValidationError.