Question

我在我的Django应用程序中制作了一些模型来描述我的应用程序中存在的不同类型的民意调查。

from django.db import models
from api.models.helpers import JSONSerializableModel
from api.models.speaker import Speaker
from api.models.auth import Attendee
from api.models.event import Event



class BasePoll(JSONSerializableModel, models.Model):

    text = models.CharField('text', max_length=300, blank=False)



class MultipleChoicePoll(JSONSerializableModel, models.Model):

    @property
    def results(self):
        results = multiplechoicepollresponse_set.all().annotate(Count('multiplechoicepollresponse'))
        return average_rating


class RatingPoll(BasePoll):
    @property
    def average(self):
        average_rating = ratingpollresponse_set.all().aggregate(Avg('rating'))
        print(average_rating)
        return average_rating


class OpenQuestionPoll(BasePoll): 
    pass

我已经进行了迁移，一切似乎都很好，但现在当我尝试使用交互式shell时：

In [6]: poll = MultipleChoicePoll.objects.all()[0]

In [7]: poll.text = 'Some poll text'

In [8]: poll.save()

In [9]: poll = MultipleChoicePoll.objects.all()[0]

In [10]: poll.text
---------------------------------------------------------------------------
AttributeError                            Traceback (most recent call last)
<ipython-input-10-28f6dbcd48ba> in <module>()
----> 1 poll.text

AttributeError: 'MultipleChoicePoll' object has no attribute 'text'

现在，当我从BasePoll继承时，每个子模型会获得一个自动的basepoll_ptr One2One字段。但是当我迁移时，它会询问此字段的默认值，这是不可能的，因为这个字段是由Django创建的，而不是我：

    You are trying to add a non-nullable field 'basepoll_ptr' to multiplechoicepoll without a default; we can't do that (the database needs something to populate existing rows).
Please select a fix:
 1) Provide a one-off default now (will be set on all existing rows with a null value for this column)
 2) Quit, and let me add a default in models.py

Django要求为继承模型的父模型提供默认链接

0 个答案: