元类与 Django 中的 modelformset_factory 冲突

Posted 2023-02-23

【中文标题】元类与 Django 中的 modelformset_factory 冲突

【英文标题】：metaclass conflict with modelformset_factory in Django

【发布时间】：2011-12-18 14:15:06

【问题描述】：

我正在使用 Django 模型继承来创建两个模型 - WorkAttachmentPicture 和 WorkAttachmentAudio

class WorkAttachment(models.Model):
    """ Abstract class that holds all fields that are required in each attachment """
    work            = models.ForeignKey(Work)
    added           = models.DateTimeField(default=datetime.datetime.now)
    views           = models.IntegerField(default=0)

    class Meta:
        abstract = True


class WorkAttachmentFileBased(WorkAttachment):
    """ Another base class, but for file based attachments """
    description     = models.CharField(max_length=500, blank=True)
    size            = models.IntegerField(verbose_name=_('size in bytes'))

    class Meta:
        abstract = True


class WorkAttachmentPicture(WorkAttachmentFileBased):
    """ Picture attached to work """
    image           = models.ImageField(upload_to='works/images', width_field='width', height_field='height')
    width           = models.IntegerField()
    height          = models.IntegerField()

class WorkAttachmentAudio(WorkAttachmentFileBased):
    """ Audio file attached to work """
    file            = models.FileField(upload_to='works/audio')

一个作品可以有多个音频和视频附件，所以我使用modelformset_factory来创建表单：

class ImageAttachmentForm(forms.ModelForm):
    """ Image attached to work """
    image = forms.FileField(
        label=_('File'),
        help_text=_('JPEG, GIF or PNG image.')
    )
    description = forms.CharField(
        widget=forms.Textarea(),
        label=_('File description'),
        help_text=_('Max. 500 symbols.'),
        max_length=500
    )

    class Meta:
        model = WorkAttachmentPicture
        fields = ['image', 'description']

ImageAttachmentFormSet = modelformset_factory(WorkAttachmentPicture, form=ImageAttachmentForm)


class AudioAttachmentForm(forms.Form):
    """ Audio file attached to work """
    file = forms.FileField(
        label=_('File'),
        help_text=_('MP3 file.')
    )
    description = forms.CharField(
        widget=forms.Textarea(),
        label=_('File description'),
        help_text=_('Max. 500 symbols.'),
        max_length=500
    )

    class Meta:
        model = WorkAttachmentAudio
        fields = ['file', 'description']

AudioAttachmentFormSet = modelformset_factory(WorkAttachmentAudio, form=AudioAttachmentForm)

对我来说一切似乎都是正确的，但在项目启动时我得到了错误：

metaclass conflict: the metaclass of a derived class must be a (non-strict) subclass of the metaclasses of all its bases

如果我只创建一个表单集（例如ImageAttachmentFormSet），一切正常。但是当我添加另一个时，会出现错误。我该如何解决这个问题，以使用带有继承模型的模型集？

【问题讨论】：

它是单独与他们每个人一起工作，还是只是 AudioAttachmentFrom 坏了？

@Autopulated 你是对的，它是 AudioAttachmentFrom。看看下面我自己的答案。

【参考方案1】：

解决了。如果你仔细看

# this has forms.ModelForm
class ImageAttachmentForm(forms.ModelForm):
# this has forms.Form
class AudioAttachmentForm(forms.Form):

我已将 forms.Form 更改为 forms.ModelForm，现在一切正常 - 这是一个简单的复制/粘贴错误。