I have the following models:
class Color(models.Model):
name = models.CharField(max_length=50, null=False, blank=False)
def __str__(self):
return self.name
class Flower(models.Model):
flower_number = models.PositiveSmallIntegerField(
default=1,blank=True, null=True)
petal_color = models.ManyToManyField(Color,blank=True, related_name="%(app_label)s_%(class)s_petal",
related_query_name="%(app_label)s_%(class)s")
petal_outer_color = models.ManyToManyField(Color,blank=True, related_name="%(app_label)s_%(class)s_petal_outer",
related_query_name="%(app_label)s_%(class)s")
class Meta:
abstract = True
class Plant(Flower):
name = models.CharField(max_length=50, null=False, blank=False, unique=True)
On the Admin I just have:
admin.site.register(Plant)
When I go into the Django admin and fill out either of the manytomany petal_color or petal_outer_color with data the other manytomany field automatically gets filled when it saves. How do I stop this from happening? Nothing shows up as an error and I tried going back and deleting and re-entering data but it still happens
Try using symmetrical=False in the ManyToManyField, that might be causing the issue here as you have two M2M fields going to the same model.
Read up on symmetrical in the Django docs.
Do something like this
class Flower(models.Model):
flower_number = models.PositiveSmallIntegerField(
default=1,blank=True, null=True)
petal_color = models.ManyToManyField(Color,blank=True, symmetrical=False related_name="%(app_label)s_%(class)s_petal",
related_query_name="%(app_label)s_%(class)s")
petal_outer_color = models.ManyToManyField(Color,blank=True, symmetrical=False, related_name="%(app_label)s_%(class)s_petal_outer",
related_query_name="%(app_label)s_%(class)s")
class Meta:
abstract = True
By default, the value of symmetrical is True for Many to Many Field which is a bi-directional relationship.
The ManyToManyField is assumed to be symmetrical – that is, if I am your friend, then you are my friend.
Related
In my app I have the following models:
class Category(BaseStampModel):
cat_id = models.AutoField(primary_key=True, verbose_name='Cat Id')
category = models.CharField(max_length=55, verbose_name='Category')
class MasterList(BaseStampModel):
master_list_id = models.AutoField(primary_key=True, verbose_name='Master List Id')
mast_list_category = models.ForeignKey(Category, on_delete=models.CASCADE, null=True, verbose_name='Category')
# Other fields ...
My BaseModel looks like this:
class BaseStampModel(models.Model):
created_by = models.ForeignKey(settings.AUTH_USER_MODEL, related_name='%(class)s_created', blank=True, null=True, on_delete=models.SET_NULL, verbose_name='Created by')
created_on = models.DateTimeField(auto_now_add = True, null=True, blank=True)
With this I am able to display the model objects and create/update instances.
In my view, when I want to retrieve the verbose_name from model "Category" using:
`model_fields = [(f.verbose_name, f.name) for f in Category._meta.get_fields()]`
I am getting the following error in my browser:
AttributeError: 'ManyToOneRel' object has no attribute 'verbose_name'
If I remove the the FK relationship from the field mast_list_category (make it a simple CharField) I don't get the error.
Gone through millions of pages, but no solution yet.
Any help is much appreciated.
You can't access the verbose_name just like accessing model fields
But there are different ways of getting verbose_name. The better way is using get_field
model._meta.get_field('field_name').verbose_name
In your case, replace the model with Category and field_name with the field you want to get the verbose_name
This is what I am doing:
Declare an empty array, loop through the model, get the field name and its verbose_name and append.
array_model_with_ver_name = []
for f in Category._meta.get_fields():
if hasattr(f, 'verbose_name'):
array_model_with_ver_name.append((f.verbose_name, f.name))
If the models are as follows,
class Subject(BaseModel):
name = models.CharField(db_column='name', max_length=200, blank=False, null=False, unique=True)
class Meta:
managed = True
db_table = 'Subject'
class Topic(BaseModel):
name = models.CharField(db_column='name', max_length=200, blank=False, null=False, unique=True)
subject = models.ForeignKey(Subject, on_delete=models.CASCADE, null=False, related_name='subject_topic')
class Meta:
managed = True
db_table = 'Topic'
class Question(BaseModel):
topic = models.ForeignKey(Topic, on_delete=models.CASCADE, null=False, related_name='question_topic')
class Meta:
managed = True
db_table = 'Question'
How can I make a query Question for a subject.
questions = Question.objects.filter(topic_in=Topic.objects.get(subject=subject).only('id').all())
but it's not working. Any help would be really great help.
Your current "inner queryset" won't give you multiple values, it only returns 1.
Topic.objects.get(subject=subject).only('id').all()
You are using .objects.get() which returns a model instance, so for example .only() or .all() on that won't work unless your model has such a defined function.
Furthermore you don't really need 2 querysets, you can get your result with only one:
my_subject_ids = [...] # these are the ids of Subject models you want
Question.objects.filter(topic__subject_id__in=my_subject_ids)
You can also query for Subject.name, just use the following for this: topic__subject__name__in=my_list.
If you want to query for a specific Subject-instance you can use topic__subject=my_obj.
You also might wanna take a look at the docs for more information on that.
These are my two models, when I try to open City page on Django I get an error: "column city.country_id_id does not exist". I don't know why python adds extra _id there.
class Country(models.Model):
country_id = models.CharField(primary_key=True,max_length=3)
country_name = models.CharField(max_length=30, blank=True, null=True)
class Meta:
managed = False
db_table = 'country'
class City(models.Model):
city_id=models.CharField(primary_key=True,max_length=3)
city_name=models.CharField(max_length=30, blank=True, null=True)
country_id = models.ForeignKey(Country, on_delete=models.CASCADE)
class Meta:
managed = False
db_table = 'city'
Because if you construct a foreign key, Django will construct a "twin field" that stores the primary key of the object. The foreign key itself is thus more a "proxy" field that fetches the object.
Therefore you normally do not add an _id suffix to the ForeignKey:
class City(models.Model):
city_id = models.CharField(primary_key=True,max_length=3)
city_name = models.CharField(max_length=30, blank=True, null=True)
country = models.ForeignKey(Country, on_delete=models.CASCADE)
class Meta:
managed = False
db_table = 'city'
It however might be better for unmanaged tables, to specify a db_column=… parameter [Djang-doc] in the ForeignKey:
class City(models.Model):
city_id = models.CharField(primary_key=True,max_length=3)
city_name = models.CharField(max_length=30, blank=True, null=True)
country = models.ForeignKey(Country, db_column='country_id', on_delete=models.CASCADE)
class Meta:
managed = False
db_table = 'city'
With this parameter you make it explicit how the column is named at the database side.
this is due to Django's behind the scenes magic.
The fields documentation is very clear about that and I highly recommend you read the Foreign Key section in the link below:
https://docs.djangoproject.com/en/3.0/ref/models/fields/#django.db.models.ForeignKey
Basically, when you want to access the Country reference in the if a City instance, you would do it like this:
city.country_id
I also recommend another naming convention for your Foreign Key fields. Instead of <modelname>_id = models.ForeignKey... just call it <modelname> = models.ForeignKey...
Hope this helps, happy coding
I'm trying to figure it out on how I can show only a specific set of dynamic fields in eav to a unique registered model in my apps.models. But I don't know how to this, I've also read the documents but I can't seem to find anything about it, or maybe I've come across it and didn't understand.
Now, what is happening is that, when I add an attribute in the django admin. It also adds the dynamic field in all the models registered in the eav.
What I want to do is that;
model 1 - dynamic_field1, dynamic_field2, dynamic_field3
model 2 - dynamic_field4, dynamic_field5, dynamic_field6
Btw, I'm currently using the django-eav2 the documentation is in the link. I've found my solution for my initial use case here link
Below codes are basically on how to register my models to the eav. Here is my sample models
class ClientName(models.Model):
name = models.CharField(max_length=250, null=True, blank=True)
description = models.TextField(null=True, blank=True)
is_active = models.BooleanField(default=True)
def __str__(self):
return str(self.name)
class CallDetails(models.Model):
client_name = models.ForeignKey(ClientName, on_delete=models.PROTECT, null=True, blank=True, db_index=True)
letter_info = models.TextField(null=True, blank=True)
def __str__(self):
return str(self.client_name)
class Meta:
verbose_name = 'Call Detail'
ordering = ['client_name']
eav.register(ClientName)
eav.register(CallDetails)
below is my admin.py
class CallDetailsAdminForm(BaseDynamicEntityForm):
model = CallDetails
class CallDetailsAdmin(BaseEntityAdmin):
form = CallDetailsAdminForm
admin.site.register(CallDetails, CallDetailsAdmin)
I have a Django model for a player of a game
class Player(models.Model):
name = models.CharField(max_length=50)
team = models.ForeignKey('Team', on_delete=models.CASCADE, blank=True, null=True)
game = models.ForeignKey('Game', on_delete=models.CASCADE)
objects = GameManager()
class Meta:
unique_together = ('name', 'game',)
I have only one unique constraint, that the name and the game are unique together.
Now, I would like to extend our page by adding registered users. So, I would add this to the model.
user = models.ForeignKey('auth.User', on_delete=models.CASCADE, blank=True, null=True)
So, an registered user can subscribe to a game by adding a name, team, game, and his/her user. However, the user should only be able to add his account once to an game, which would be a second unique constrain
unique_together = ('user', 'game',)
Is it possible to give in Django two unique constraints to the model? Or do I have to search in the table manually prior to saving the new entries? Or is there a better way?
Yes, in fact by default unique_together is a collection of collections of fields that are unique together, so something like:
class Player(models.Model):
name = models.CharField(max_length=50)
team = models.ForeignKey('Team', on_delete=models.CASCADE, blank=True, null=True)
game = models.ForeignKey('Game', on_delete=models.CASCADE)
objects = GameManager()
class Meta:
unique_together = (('name', 'game',), ('user', 'game',))
Here we thus specify that every name, game pair is unique, and every user, game pair is unique. So it is impossible to create two Player objects for the same user and game, or for the same game and name.
It is only because a single unique_together constraint is quite common, that one can also pass a single collection of field names that should be unique together, as is written in the documentation on Options.unique_together [Django-doc]:
Sets of field names that, taken together, must be unique:
unique_together = (("driver", "restaurant"),)
This is a tuple of tuples that must be unique when considered
together. It's used in the Django admin and is enforced at the
database level (i.e., the appropriate UNIQUE statements are included
in the CREATE TABLE statement).
For convenience, unique_together can be a single tuple when dealing with a single set of fields:
unique_together = ("driver", "restaurant")
You should use models.UniqueConstraint (reference).
As noted in the reference:
UniqueConstraint provides more functionality than unique_together. unique_together may be deprecated in the future.
Do this:
class Meta:
constraints = [
models.UniqueConstraint(fields=['name', 'game'], name="unique_name_game"),
models.UniqueConstraint(fields=['user', 'game'], name="unique_user_game"),
]
For example please refer to this :-
class Stores(models.Model):
name = models.CharField(max_length=50)
address = models.CharField(max_length=50)
lat = models.FloatField()
lng = models.FloatField()
merchant = models.ForeignKey(Profile, on_delete=models.CASCADE, related_name="stores")
def __str__(self):
return "{}: {}".format(self.name, self.address)
class Meta:
verbose_name_plural = 'Stores'
class Items(models.Model):
name = models.CharField(max_length=50, unique=False)
price = models.IntegerField()
description = models.TextField()
stores = models.ForeignKey(Stores, on_delete=models.CASCADE, related_name="items")
def __str__(self):
return self.name
class Meta:
verbose_name_plural = "Items"
unique_together = ('name', 'stores',)