如何删除Django中的相关模型(多对多)？

Question

我在Django中有两个模型，我使用它们来存储一些文档，并为文档中的单词建立索引。以下是一些模型：

class DMS_Dokument(models.Model):
    dms_dok_titel = models.CharField(max_length=255, blank=True)
    dms_dok_beschreibung = models.CharField(max_length=3000, blank=True, null=True)
    dms_dok_datei = models.FileField(max_length=255,upload_to='DMS/')
    dms_dok_hochgeladen_am = models.DateField()
    dms_dok_indiziert = models.BooleanField(default=False)
    dms_dok_gehoert_zu_app = models.CharField(max_length=255, choices=app_choices, blank=False, null=False)
    dms_dok_typ = models.CharField(max_length=255, choices=typ_choices, blank=False, null=False, default='Sonstiges')

    def save(self, *args, **kwargs):
        preserve_ext = extension(self.dms_dok_datei.name)
        neuer_dateiname = self.dms_dok_gehoert_zu_app + '_' + self.dms_dok_titel + '_' + self.dms_dok_hochgeladen_am.strftime("%d.%m.%Y")
        self.dms_dok_datei.name = neuer_dateiname + preserve_ext
        super(DMS_Dokument, self).save(*args, **kwargs)

    class Meta:
        app_label = 'DMS'

class DMS_Index_Data(models.Model):
    dms_ind_wort = models.CharField(max_length=255, blank=False, null=True)
    dms_ind_m2m = models.ManyToManyField(DMS_Dokument, related_name='indexes')
    #dms_ind_dok_fk = models.ForeignKey('DMS_Dokument', on_delete=models.CASCADE)

    class Meta:
        app_label = 'DMS'
        ordering = ['dms_ind_wort']

现在，当我使用DeleteView删除DMS_Dokument对象时，可以正确地将其从数据库中删除。但是另一个表中的条目仍然存在。我如何告诉Django，在删除文档时，索引也应该从与其相关的条目中清除？这是特殊的吗，因为我有多对多的关系？

Answer 1

您可以用覆盖save()方法的相同方式覆盖模型上的delete()方法。

如果您希望每次都删除m2m数据，那么覆盖delete()方法是一个好主意。

class DMS_Dokument(models.Model):
    ...

    def save(self, *args, **kwargs):
        preserve_ext = extension(self.dms_dok_datei.name)
        neuer_dateiname = self.dms_dok_gehoert_zu_app + '_' + self.dms_dok_titel + '_' + self.dms_dok_hochgeladen_am.strftime("%d.%m.%Y")
        self.dms_dok_datei.name = neuer_dateiname + preserve_ext
        super(DMS_Dokument, self).save(*args, **kwargs)

    def delete(self):
        self.indexes.all().delete()
        super(DMS_Dokument, self).delete()

    class Meta:
        app_label = 'DMS'

您也可以只覆盖DeleteViewe的delete()方法

from django.shortcuts import get_object_or_404

def delete(self, request, *args, **kwargs):
    # get the DMS_Dokument pk. you might need to change this depending on your view
    instance_pk = self.kwargs['pk']
    instance = get_object_or_404(DMS_Dokument, pk=instance_pk)

    # delete the m2m first
    instance.indexes.all().delete()

    # delete the instance itself
    instance.delete()