class Professional(models.Model):
...
favoriting_customers = models.ManyToManyField(
'customers.Customer', blank=True,
through='favorites.FavoriteProfessional')
recommending_customers = models.ManyToManyField(
'customers.Customer', blank=True,
through='recommendations.ProfessionalRecommendation')
I get no errors when I delete on of the ManyToMany fields. However, I get SystemCheckError when I run 'python manage.py makemigrations'.
ERRORS:
professionals.Professional.favoriting_customers: (fields.E304) Reverse accessor for 'Professional.favoriting_customers' clashes with reverse accessor for 'Professional.recommending_customers'.
HINT: Add or change a related_name argument to the definition for 'Professional.favoriting_customers' or 'Professional.recommending_customers'.
professionals.Professional.recommending_customers: (fields.E304) Reverse accessor for 'Professional.recommending_customers' clashes with reverse accessor for 'Professional.favoriting_customers'.
HINT: Add or change a related_name argument to the definition for 'Professional.recommending_customers' or 'Professional.favoriting_customers'.
As suggested by the HINT, you need to use related_name to avoid clashes on backward relations. You are going to need this every time you have two fields in the same model with a relation to the same object (customers.Customer in your case).
You can try something like this:
class Professional(models.Model):
...
favoriting_customers = models.ManyToManyField(
'customers.Customer', blank=True,
through='favorites.FavoriteProfessional',
related_name='favorites'
)
recommending_customers = models.ManyToManyField(
'customers.Customer', blank=True,
through='recommendations.ProfessionalRecommendation',
related_name='recommendations'
)
If you are not interested in backward relation to Professional table, you can disable it by using '+' as the related_name:
class Professional(models.Model):
...
favoriting_customers = models.ManyToManyField(
'customers.Customer', blank=True,
through='favorites.FavoriteProfessional',
related_name='+'
)
recommending_customers = models.ManyToManyField(
'customers.Customer', blank=True,
through='recommendations.ProfessionalRecommendation',
related_name='+'
)
Also, you should be careful with related_name
Related
I have:
class Direction(models.Model):
left = models.OneToOneField(
'self', on_delete=models.SET_NULL, null=True, related_name='right')
right = models.OneToOneField(
'self', on_delete=models.SET_NULL, null=True, related_name='left')
The error:
ant.Direction.left: (fields.E302) Reverse accessor for 'ant.Direction.left' clashes with field name 'ant.Direction.right'.
HINT: Rename field 'ant.Direction.right', or add/change a related_name argument to the definition for field 'ant.Direction.left'.
How does one make this relationship so that a.left = b and b.right = a?
You can not use as related_name the same as the fields that have been defined. You likely do not want to work with two OneToOneFields anyway, you can define a single OneToOneField, and set the related name to the opposite, so:
class Direction(models.Model):
left = models.OneToOneField(
'self',
on_delete=models.SET_NULL,
null=True,
related_name='right'
)
# no right
So now if a direction a has as .left a direction b, then b has as .right the object a.
If there is no .right, then accessing .right will raise a Direction.DoesNotExist exception, we can however fix this issue by making use of another for the related_name, and work with a property that will wrap it in a try-except:
class Direction(models.Model):
left = models.OneToOneField(
'self',
on_delete=models.SET_NULL,
null=True,
related_name='_right'
)
#property
def right(self):
try:
return self._right
except Direction.DoesNotExist:
return None
#right.setter
def _set_right(self, value):
self._right = value
I am building a platform with 3 users roles: Admin, Creator and Brand. I redefined a default django User to be able to login by email.
class AbstractUser(AbstractBaseUser, PermissionsMixin):
email = models.EmailField(max_length=32, unique=True)
first_name = models.CharField(max_length=32, blank=True)
last_name = models.CharField(max_length=64, blank=True)
is_staff = models.BooleanField(default=False)
is_superuser = models.BooleanField(default=False)
is_active = models.BooleanField(default=True)
date_joined = models.DateTimeField(auto_now_add=True)
location = models.CharField(max_length=120, blank=True)
bio = models.TextField(blank=True)
USERNAME_FIELD = 'email'
EMAIL_FIELD = 'email'
REQUIRED_FIELDS = []
objects = CustomUserManager()
class Meta:
abstract = True
def __str__(self):
return self.email
I made this class an abstract one to be able to add new classes, inherit from the Abstract class and redefine their attributes.
class PlatformAdmin(AbstractUser):
pass
class Creator(AbstractUser):
email = models.EmailField(max_length=32, unique=True, error_messages={
'unique': "A customer with that email already exists.",
})
class Brand(AbstractUser):
name = models.CharField(max_length=64)
I also add in settings.py following:
AUTH_USER_MODEL = 'users.PlatformAdmin'
Now when I run makemigrations it will give the following output:
users.Brand.groups: (fields.E304) Reverse accessor for 'Brand.groups' clashes with reverse accessor for 'Creator.groups'.
HINT: Add or change a related_name argument to the definition for 'Brand.groups' or 'Creator.groups'.
users.Brand.groups: (fields.E304) Reverse accessor for 'Brand.groups' clashes with reverse accessor for 'PlatformAdmin.groups'.
HINT: Add or change a related_name argument to the definition for 'Brand.groups' or 'PlatformAdmin.groups'.
users.Brand.user_permissions: (fields.E304) Reverse accessor for 'Brand.user_permissions' clashes with reverse accessor for 'Creator.user_permissions'.
HINT: Add or change a related_name argument to the definition for 'Brand.user_permissions' or 'Creator.user_permissions'.
users.Brand.user_permissions: (fields.E304) Reverse accessor for 'Brand.user_permissions' clashes with reverse accessor for 'PlatformAdmin.user_permissions'.
HINT: Add or change a related_name argument to the definition for 'Brand.user_permissions' or 'PlatformAdmin.user_permissions'.
users.Creator.groups: (fields.E304) Reverse accessor for 'Creator.groups' clashes with reverse accessor for 'Brand.groups'.
HINT: Add or change a related_name argument to the definition for 'Creator.groups' or 'Brand.groups'.
users.Creator.groups: (fields.E304) Reverse accessor for 'Creator.groups' clashes with reverse accessor for 'PlatformAdmin.groups'.
HINT: Add or change a related_name argument to the definition for 'Creator.groups' or 'PlatformAdmin.groups'.
users.Creator.user_permissions: (fields.E304) Reverse accessor for 'Creator.user_permissions' clashes with reverse accessor for 'Brand.user_permissions'.
HINT: Add or change a related_name argument to the definition for 'Creator.user_permissions' or 'Brand.user_permissions'.
users.Creator.user_permissions: (fields.E304) Reverse accessor for 'Creator.user_permissions' clashes with reverse accessor for 'PlatformAdmin.user_permissions'.
HINT: Add or change a related_name argument to the definition for 'Creator.user_permissions' or 'PlatformAdmin.user_permissions'.
users.PlatformAdmin.groups: (fields.E304) Reverse accessor for 'PlatformAdmin.groups' clashes with reverse accessor for 'Brand.groups'.
HINT: Add or change a related_name argument to the definition for 'PlatformAdmin.groups' or 'Brand.groups'.
users.PlatformAdmin.groups: (fields.E304) Reverse accessor for 'PlatformAdmin.groups' clashes with reverse accessor for 'Creator.groups'.
HINT: Add or change a related_name argument to the definition for 'PlatformAdmin.groups' or 'Creator.groups'.
users.PlatformAdmin.user_permissions: (fields.E304) Reverse accessor for 'PlatformAdmin.user_permissions' clashes with reverse accessor for 'Brand.user_permissions'.
HINT: Add or change a related_name argument to the definition for 'PlatformAdmin.user_permissions' or 'Brand.user_permissions'.
users.PlatformAdmin.user_permissions: (fields.E304) Reverse accessor for 'PlatformAdmin.user_permissions' clashes with reverse accessor for 'Creator.user_permissions'.
HINT: Add or change a related_name argument to the definition for 'PlatformAdmin.user_permissions' or 'Creator.user_permissions'.
I can't figure out what I am doing wrong and how to solve this issue.
I think you have to add 3 fields like this:
class AbstractUser(AbstractBaseUser, PermissionsMixin):
email = models.EmailField(max_length=32, unique=True)
first_name = models.CharField(max_length=32, blank=True)
last_name = models.CharField(max_length=64, blank=True)
is_staff = models.BooleanField(default=False)
is_superuser = models.BooleanField(default=False)
is_active = models.BooleanField(default=True)
date_joined = models.DateTimeField(auto_now_add=True)
location = models.CharField(max_length=120, blank=True)
bio = models.TextField(blank=True)
# add this 3 fields
is_admin = models.BooleanField(default=False)
is_creater = models.BooleanField(default=False)
is_brand = models.BooleanField(default=True)
USERNAME_FIELD = 'email'
EMAIL_FIELD = 'email'
REQUIRED_FIELDS = []
objects = CustomUserManager()
class Meta:
abstract = True
def __str__(self):
return self.email
AUTH_USER_MODEL = 'users.CustomUserModel'
I think you have to follow this method.
inside AbstractUser in class Meta, abstract=True is creating the problem. also you are repeating the email field in 2 places (AbstractUser and Creator).
OR
keep only one user model(PlatformAdmin). convert Creator and Brand as normal model. otherwise fields from PermissionsMixin class are clashing(same fields are repeating in multiple places).
I am trying to create a db model using django inspect db and it is generating all the models but I am getting error.
I am using this command to generate db models for existing database:
python manage.py inspectdb > models.py
It is generating models accurately but in fileds such as this:
create_uid = models.ForeignKey('self', models.DO_NOTHING,db_column='create_uid', blank=True, null=True)
write_uid = models.ForeignKey('self',models.DO_NOTHING, db_column='write_uid', blank=True, null=True)
I am getting error:
polls.ResUsers.create_uid: (fields.E304) Reverse accessor for 'ResUsers.create_uid' clashes with reverse accessor for 'ResUsers.write_uid'.
HINT: Add or change a related_name argument to the definition for 'ResUsers.create_uid' or 'ResUsers.write_uid'.
polls.ResUsers.write_uid: (fields.E304) Reverse accessor for 'ResUsers.write_uid' clashes with reverse accessor for 'ResUsers.create_uid'.
HINT: Add or change a related_name argument to the definition for 'ResUsers.write_uid' or 'ResUsers.create_uid'.
I am adding related names like this:
create_uid = models.ForeignKey('self', models.DO_NOTHING,related_name='create_uid',db_column='create_uid', blank=True, null=True)
What should I do in order to use generated models. I am using postgres.
I am updating my question one of the answer worked for me when I am using it like this:
create_uid = models.ForeignKey(
'self',
models.DO_NOTHING,
db_column='create_uid',
related_name='created_items',
blank=True,
null=True
)
In one other model class when I am using this code like this:
create_uid = models.ForeignKey(
'ResUsers',
models.DO_NOTHING,
db_column='create_uid',
related_name='created_items',
blank=True,
null=True
)
I am getting the error:
polls.ResUsers.create_uid: (fields.E304) Reverse accessor for 'ResUsers.create_uid' clashes with reverse accessor for 'SurveyUserInput.create_uid'.
HINT: Add or change a related_name argument to the definition for 'ResUsers.create_uid' or 'SurveyUserInput.create_uid'.
The related_name=… [Django-doc] is the name of the relation in reverse. So it is meant to access all model objects with as create_uid/write_uid the object. This can result in a QuerySet of zero, one or more elements.
Therefore the related_names of two ForeignKeys to the same model, can not be the same, since that would make the model ambiguous. Since your ForeignKeys refer to the 'self' model, you can not even given these the name of a field that already exists.
You thus might want to give the relations a name like:
class MyModel(models.Model):
create_uid = models.ForeignKey(
'self',
models.DO_NOTHING,
db_column='create_uid',
related_name='created_items',
blank=True,
null=True
)
write_uid = models.ForeignKey(
'self',
models.DO_NOTHING,
db_column='write_uid',
related_name='written_items',
blank=True,
null=True
)
I've recieved the following error and I'm not sure how to handle this in my model.
HINT: Add or change a related_name argument to the definition for 'UserCart.state_tax' or 'UserCart.fed_tax'.
userorders.UserCart.state_tax: (fields.E304) Reverse accessor for 'UserCart.state_tax' clashes with reverse accessor for 'UserCart.other_tax'.
models.py
class UserCart(models.Model):
user = models.ForeignKey(User, on_delete=models.CASCADE, default=None)
state_tax = models.ForeignKey(Tax, on_delete=models.SET_NULL, null=True)
fed_tax = models.ForeignKey(Tax, on_delete=models.SET_NULL, null=True)
This is here necessary, since you have two references from UserCart to the Tax model. This thus means that the relation in reverse (from Tax to UserCart) can not be usercart_set, since then it is not clear which relation we use in reverse.
We thus should at least give a related name to one of the relations (that is different from usercart_set). For example:
from django.contrib.auth import get_user_model
class UserCart(models.Model):
user = models.ForeignKey(get_user_model(), on_delete=models.CASCADE, default=None)
state_tax = models.ForeignKey(
Tax,
related_name='state_usercarts',
on_delete=models.SET_NULL,
null=True
)
fed_tax = models.ForeignKey(
Tax,
related_name='fed_usercarts',
on_delete=models.SET_NULL,
null=True
)
Note: you might want to make use of get_user_model [Django-doc] over a reference to User itself. If you later change your user model, then the ForeignKey will automatically refer to the new user model.
How do you define the reverse relation from another object to this one with a '+' as it's related name?
class FeaturedContentPage(Page):
featured_page = models.ForeignKey(
'wagtailcore.Page',
null=True,
blank=True,
on_delete=models.SET_NULL,
related_name='+',
)
The idea of a related_name*ending with a '+' is to disable creating a reverse relation, as is documented:
If youd prefer Django not to create a backwards relation, set related_name to '+' or end it with '+'.
You can of course still query in reverse with:
FeaturedContentPage.objects.filter(featured_page=my_page)
But there is thus no relation constructed in reverse, so my_page.featuredcontentpage_setis not accessible.
the related_name argument is used for reverse relation name . if a model has 2 field referencing the same model
featured_page = models.ForeignKey(
'wagtailcore.Page',
null=True,
blank=True,
on_delete=models.SET_NULL,
related_name='+',
)
regular_page = models.ForeignKey(
'wagtailcore.Page',
null=True,
blank=True,
on_delete=models.SET_NULL,
related_name='+',
)
without related_name='+' django will complain because it use wagtailcore.Page model name for reverse relation. as two attribute in object can not have same name by setting related_name='+' to one or both field will ignore creating reverse relation .