在Django中保存表单数据之前进行重复检查

时间:2012-10-18 18:04:50

标签: django forms

我收到了以下表格:

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

正如您所看到的,我覆盖了clean方法,以检查当用户尝试添加该课程时,该课程是否已存在于数据库中。这对我来说很好。

但是,当我想为表单添加相同的检查以进行编辑时,问题就出现了。因为它正在编辑,所以DB中已存在具有相同课程名称的记录。因此,相同的检查会抛出课程名称已经存在的错误。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。如果它已被更改,我可以执行与上面相同的检查。如果没有更改,我不需要进行检查。但我不知道如何获取原始数据进行编辑。

有没有人知道如何在Django中执行此操作?

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。

2 个答案:

答案 0 :(得分:3)

我相信从结果中排除当前实例ID可以解决问题:

from django.db.models import Q
try:
    qs = Course.objects.filter(name=self.cleaned_data.get('name'))
    if self.instance.pk is not None:
        qs = qs.filter(~Q(pk=self.instance.pk))
    course = qs.get()
except Course.DoesNotExist:
    course = None

然而正如dokkaebi指出的那样,独特的确是更好的方法,因为这种解决方案容易受到竞争条件的影响。我不确定你的数据模型是什么样的,但我怀疑定义

class Meta:
    unique_together = ('department', 'name')

应该完成你想要的。

答案 1 :(得分:2)

我认为您应该在unique=True字段上设置Course.name,让框架为您处理验证。

<强>更新

由于unique=True不是您的案例的正确答案,您可以这样检查:

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