CODEWITHSUNDEEP
djangodjango-models
user1711168
user1711168

Reputation: 707

deleting related models django

i currently have this models how do i delete the logo without deleting the company model.Please sample codes if possible thanks.

class Picture(models.Model):
    owner = models.ForeignKey(User,blank = True)
    caption = models.CharField(max_length=150, blank=True, null=True)
    image = ImageField(upload_to='images/',blank = True, null = True)

class Company(GenericUser):
    company_name = models.CharField(max_length=150,blank = True,null = True)
    logo = models.ForeignKey(Picture,blank = True,null = True)

this is a model how will i then remove the foto from the land model the model looks like this.

class Land(Properies):
    photo = models.ManyToManyField(Picture,blank=True,related_name='Land_Pictures',null = True)

i tried this bit it dose not work

checked_list = []
start = 1            
land_photos = sorted(list(land.photo.select_related()),reverse =True)
while start < 8:
    photo = 'photo%s' % start
    checked = form.cleaned_data[photo]
    if checked != None:
        checked_list.append(land_photos[start - 1])
        start += 1            
for a_foto in checked_list:
land.photo.remove(a_foto)
try:
    a_foto.remove_all_file()
    a_foto.delete()
except OSError:
    pass

i keep getting an error like that id is set to none and if i hit refresh it works i think

Exception Type:     AssertionError
Exception Value:    
Picture object can't be deleted because its id attribute is set to None.

Upvotes: 1

Views: 6310

Answers (3)

Daniel Hepper
Daniel Hepper

Reputation: 29967

You have to clear the references from any Company objects to the Picture object you want to delete.

logo = company.logo
company.logo = None
logo.delete()

However, if a Picture is referenced by multiple Companies, try this:

logo = Picture.object.get(...) # the Picture you want to delete
logo.company_set.update(logo=None)
logo.delete()

You should also consider changing the reference from Company to Image so related instances do not get deleted by default.

class Company(GenericUser):
    company_name = models.CharField(max_length=150,blank = True,null = True)
    logo = models.ForeignKey(Picture,blank = True,null = True, on_delete=models.SET_NULL)

Upvotes: 2

Williams
Williams

Reputation: 4318

Is there any reason:

a) you are using (GenericUser)? This will undoubtedly cause you problems.

b) can't just delete the attribute (per below) and then migrate the data?

class Picture(models.Model):
    owner = models.ForeignKey(User,blank = True)
    caption = models.CharField(max_length=150, blank=True, null=True)
    image = ImageField(upload_to='images/',blank = True, null = True)

class Company(models.Model):
    company_name = models.CharField(max_length=150, blank=True, null=True)
    logo = models.ForeignKey(Picture, blank=True, null=True)

or are you trying to delete a related instance per here: https://docs.djangoproject.com/en/dev/ref/models/relations/#django.db.models.fields.related.RelatedManager.remove

In which case you'd use remove().

Upvotes: 0

rafek
rafek

Reputation: 635

Change your Company model this way:

class Company(GenericUser):
    company_name = models.CharField(max_length=150,blank = True,null = True)
    logo = models.ForeignKey(Picture,blank = True,null = True, on_delete=models.SET_NULL)

docs: https://docs.djangoproject.com/en/dev/ref/models/fields/#django.db.models.ForeignKey.on_delete

Upvotes: 2

Related Questions