CODEWITHSUNDEEP
djangomany-to-many
MDoe
MDoe

Reputation: 193

How can I delete related models in Django (many-to-many)?

I have two models in Django, which I use for storing some document and also to build an index of the words within the documents. Here are there models:

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']

When I now use a DeleteView to delete a DMS_Dokument object, then this is correctly removed from the database. But the entries in the other table remain. How can I tell Django that upon removing a document, the index should also be cleaned from entries relating to it? And is this special, as I have many-to-many relationships?

Upvotes: 0

Views: 328

Answers (1)

Navid Zarepak
Navid Zarepak

Reputation: 4208

You can override the delete() method on your models the same way you override the save() method.

Overriding the delete() method is a good idea if you want the m2m data to be deleted every time with no exception.

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'

You can also just override the delete() method for your DeleteViewe:

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()

Upvotes: 1

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