Django Model validate_unique method don't raise ValidationError - django

Question

My model is :
class Inventory(models.Model):
canteen_id = models.IntegerField()
item = models.OneToOneField('Info',db_column='item_id')
I want item should be unique for each canteen_id. I used unique_togetherbut its not working as item is in OneToOneField.
I am using validate_unique method for my model and my code is now:
class Inventory(models.Model):
canteen_id = models.IntegerField()
item = models.OneToOneField('Info',db_column='item_id')
unit_price = models.CharField(max_length=50)
quantity = models.PositiveIntegerField(default=1)
sales_vat = models.DecimalField(decimal_places=2,max_digits=5,default=0.0)
date_time = models.DateField(auto_now=False,auto_now_add=True)
def vat_count(self):
self.item_price = Decimal(self.unit_price)
self.vat = (self.item_price * 15)/100
return self.vat
def validate_unique(self, exclude=None):
qs = Inventory.objects.filter(canteen_id=self.canteen_id)
if self.pk is None:
if qs.filter(item=self.item).exists():
raise ValidationError("item already exists")
def save(self, *args,**kwargs):
self.canteen_id = CANTEEN_ID
self.sales_vat = self.vat_count()
self.unit_price = Decimal(self.unit_price)
self.validate_unique()
super(Inventory,self).save(*args, **kwargs)
Now when I am trying to add same item and canteen_id, it don't raise any error message in form page. It shows error. Error:
Environment:
Request Method: POST
Request URL: http://localhost:8000/admin/item/inventory/add/
Django Version: 1.9.2
Python Version: 2.7.6
Installed Applications:
['django.contrib.admin',
'django.contrib.auth',
'django.contrib.contenttypes',
'django.contrib.sessions',
'django.contrib.messages',
'django.contrib.staticfiles',
'item',
'bill',
'system']
Installed Middleware:
['django.middleware.security.SecurityMiddleware',
'django.contrib.sessions.middleware.SessionMiddleware',
'django.middleware.common.CommonMiddleware',
'django.middleware.csrf.CsrfViewMiddleware',
'django.contrib.auth.middleware.AuthenticationMiddleware',
'django.contrib.auth.middleware.SessionAuthenticationMiddleware',
'django.contrib.messages.middleware.MessageMiddleware',
'django.middleware.clickjacking.XFrameOptionsMiddleware']
Traceback:
File "/usr/local/lib/python2.7/dist-packages/django/core/handlers/base.py" in get_response
149. response = self.process_exception_by_middleware(e, request)
File "/usr/local/lib/python2.7/dist-packages/django/core/handlers/base.py" in get_response
147. response = wrapped_callback(request, *callback_args, **callback_kwargs)
File "/usr/local/lib/python2.7/dist-packages/django/contrib/admin/options.py" in wrapper
541. return self.admin_site.admin_view(view)(*args, **kwargs)
File "/usr/local/lib/python2.7/dist-packages/django/utils/decorators.py" in _wrapped_view
149. response = view_func(request, *args, **kwargs)
File "/usr/local/lib/python2.7/dist-packages/django/views/decorators/cache.py" in _wrapped_view_func
57. response = view_func(request, *args, **kwargs)
File "/usr/local/lib/python2.7/dist-packages/django/contrib/admin/sites.py" in inner
244. return view(request, *args, **kwargs)
File "/usr/local/lib/python2.7/dist-packages/django/contrib/admin/options.py" in add_view
1437. return self.changeform_view(request, None, form_url, extra_context)
File "/usr/local/lib/python2.7/dist-packages/django/utils/decorators.py" in _wrapper
67. return bound_func(*args, **kwargs)
File "/usr/local/lib/python2.7/dist-packages/django/utils/decorators.py" in _wrapped_view
149. response = view_func(request, *args, **kwargs)
File "/usr/local/lib/python2.7/dist-packages/django/utils/decorators.py" in bound_func
63. return func.__get__(self, type(self))(*args2, **kwargs2)
File "/usr/local/lib/python2.7/dist-packages/django/utils/decorators.py" in inner
184. return func(*args, **kwargs)
File "/usr/local/lib/python2.7/dist-packages/django/contrib/admin/options.py" in changeform_view
1378. self.save_model(request, new_object, form, not add)
File "/usr/local/lib/python2.7/dist-packages/django/contrib/admin/options.py" in save_model
991. obj.save()
File "/home/harun/Desktop/nutboltu/canteenLatest/CanteenKiosk/diucanteen/item/models.py" in save
34. self.validate_unique()
File "/home/harun/Desktop/nutboltu/canteenLatest/CanteenKiosk/diucanteen/item/models.py" in validate_unique
27. raise ValidationError("item already exists")
Exception Type: ValidationError at /admin/item/inventory/add/
Exception Value: [u'item already exists']
What is the solution???

Answer 1

If you override validate_unique method in your model you should call super as you do in save/delete etc.
def validate_unique(self, exclude=None):
# custom logic
super(Inventory, self).validate_unique(exclude=exclude)

Answer 2

Thanks all to help me find out my problem. My code was correct but I made a mistake in query. I am getting canteen_id value by assigning a variable CANTEEN_ID in settings.py and save it by save() method.
So, My query should be:
from projectdir.settings import CANTEEN_ID
def validate_unique(self,exclude=None):
qs = Inventory.objects.filter(canteen_id=CANTEEN_ID)

Answer 3

Firstly, I think unique_together should work with a one to one field. If you can create a simple test case that shows that it doesn't, then it would be worth creating a bug report.
If you do want to check the unique constraint manually, don't do it in the save() method. The Django admin doesn't expect a validation error to be raised in the save method, so you get the error. Instead, override the model's clean method, and do the check in. Model forms, including the ones in the Django admin, will call the clean method when processing the form data.
class Inventory(models.Model):
...
def clean(self):
qs = Inventory.objects.filter(canteen_id=self.canteen_id)
if self.pk is None:
if qs.filter(item=self.item).exists():
raise ValidationError("item already exists")
See the docs on validating objects for more info.

Answer 4

The way CANTEEN_ID is provided for save method may hide solution.