I'm trying to prevent users from multiple votes. So I wanna add users to ManyToManyField of the Question object. But when I go to admin all users are added to the field not the voted ones. Here is my Model's code
class Question(models.Model):
question_text = models.CharField(max_length=200)
pub_date = models.DateTimeField('date published')
choice_number = models.IntegerField(default=2)
category = models.CharField(max_length=50, default="comparison")
users = models.ManyToManyField(User, blank=True)
def subscribe(cls, current_user, new_vote):
new_vote.users.add(current_user)
And here is the function for add users to questions in views.py :
def change_vote(request, instruction, pk):
question = Question.objects.get(pk=pk)
Question.subscribe(request.user, question)
Use question.users.all() to get users related to the question
Related
I have two models, Product and Price. I have used the ForeignKey association of the Django models to define the association between product and price. the scenario is, one product can have multiple prices according to size. On the home page, I have to fetch all the products with their prices and need to show their price(probably base price).
Following is the code that I tried.
class Product(BaseModel):
name = models.CharField(max_length=50)
category = models.ForeignKey(Category, null=True, on_delete=models.SET_NULL, help_text='Please add new category if not given.')
image = models.ImageField(upload_to='images/')
tag = models.ManyToManyField(Tag, help_text='You can add multiple tags')
slug = models.SlugField(unique=True, null=True)
time = models.TimeField(verbose_name='Time Required')
class Price(BaseModel):
product = models.ForeignKey(Product, on_delete=models.CASCADE)
size = models.FloatField(validators=[MinValueValidator(0)])
amount = models.FloatField(validators=[MinValueValidator(0)])
Then in the view.py file
class ProductListView(ListView):
model = Product
context_object_name = 'products'
paginate_by = 32
def get_context_data(self,*args, **kwargs):
object = super(ProductListView, self).get_context_data(*args, **kwargs)
object['categories'] = Category.objects.order_by('name')
return object
def get_queryset(self):
return Product.objects.order_by('name')
In the template, I am able to get and loop through the categories and products but I am not able to access the related prices of each product.
If I tried something in the get_context_data, will it cause N+1 queries to fetch prices for every product?
In the template I tried to use something like {{ product.price_set }} but it returns order.Price.None.
use {{ product.price_set.all }}.
To avoid N+1 queries in your filter, use prefetch_related so it looks something like.
Product.objects.all().prefetch_related('price_set')
See prefetch_related in the Django documentation.
See also select related vs prefetch related
I'm trying to create an Django ORM query to replace a really messy raw SQL query i've written in the past but i'm not sure if Django ORM can let me do it. I have three tables:
contacts
custom_fields
custom_field_data
What I'm hoping to be able to do with the ORM is create an output as if i've queryied one single table like this:
Is such a thing possible with the ORM?
EDIT:
The models are:
class Contact(models.Model):
company = models.ForeignKey(Company, on_delete=models.PROTECT, null=True, blank=True)
class CustomField(models.Model):
name = models.CharField(max_length=100)
company = models.ForeignKey(Company, on_delete=models.PROTECT, null=False, blank=False)
class ContactCustomFieldValue(models.Model):
custom_field = models.ForeignKey(CustomField, on_delete=models.PROTECT, related_name='contact_values')
contact = models.ForeignKey(Contact, on_delete=models.PROTECT, related_name='custom_field_values', null=True)
value = models.TextField(null=True)
Solved this one in large part thanks to Ken from the Django forums.
The solution he provided looked like this:
subquery1 = Subquery(ContactCustomFieldValue.objects.filter(contact=OuterRef('id'), custom_field_id=1).values_list('value'))
subquery2 = ...
subquery3 = ...
subquery4 = ...
contact_list = Contact.objects.filter(...).annotate(field1=subquery1, ...)
I've built on it to fit my needs but as a starting point this was perfect
I need help for something, I want to call models with ManyToManyField.
I want to have method to get Class A from Class B, and another in Class B to get Class A.
here's my (shortened) code :
class Licence(models.Model):
name = models.CharField(max_length=64)
picture = models.ImageField(upload_to='finder/static/finder/img/licence/',null=True, blank=True)
description = models.TextField(null=True, blank=True)
#returns a list of games from this license
def getGamesOnThisLicence(self):
#i don't know how to proceed
class Game(models.Model):
name = models.CharField(max_length=64)
description = models.TextField()
release_date = models.DateField(null=True, blank=True)
licence = models.ManyToManyField(Licence, blank=True, null=True)
#return name of licence to which the game belongs
def getLicenceName(self):
return self.licence.name
You can access the Games with:
my_license.game_set.all()
so you can use self in the getGamesOnThisLicense, but probably there is not much gain to define a function since this makes accessing the Games already quite convenient.
Perhaps you however want to transform the ManyToManyField into a ForeignKey to License since self.license.name makes not much sense: for a ManyToManyField, self.license is a Manager over License objects that can manage zero, one or more Licenses, so you can not use self.license.name.
I'm writing a web application (DRF + Vue.js) where frontend should have an ability to narrow down GET request results via different filters.
For example, I have a model like this:
class Human(models.Model):
first_name = models.CharField(_('first name'), max_length=50, null=True, blank=True)
last_name = models.CharField(_('last name'), max_length=50, null=True, blank=True)
birth_date = models.DateField(_('birth date'), blank=True, null=True)
city = models.ForeignKey('City', on_delete=models.SET_NULL, blank=True, null=True)
phone_number = models.ForeignKey('Contact' on_delete=models.SET_NULL, blank=True, null=True)
#property
def full_name(self):
# Last name + First name
return ' '.join(str(x) for x in (self.last_name, self.first_name) if x)
#property
def is_adult(self):
now = timezone.now()
if self.birth_date:
if now.year - self.birth_date.year - \
((now.month, now.day) < (self.birth_date.month, self.birth_date.day)) >= 18:
return True
return False
Now I have simple CRUD ViewSet where I can use a list of search_fields to search by all needed fields (in my case that's birth_date, city, phone_number and full_name/is_adult). But here next problems arise:
Using search_fields I can do a search only by all fields specified in the ViewSet's search_fields (frontend can't search only by city or other distinct fields if it wants to) - other way I'll need to create a separate ViewSet (and separate URL?) for every combination of fields to filter by. Terrific.
So it looks like the correct decision must be capable of filtering by several GET parameters at once. Ideally - with opportunity to choose exact/icontains/etc comparison method on each query.
That sounds like a work for django-filter but I'm not sure yet.
It's impossible to search/filter by full_name or is_adult because they are dynamic model properties, not usual fields.
So it looks like instead of using model properties I need to use separate QuerySets (Manager methods?) that will do the logic of fiddling with model fields and creating the filtered result.
But for now I didn't find a way to choose different QuerySets in a single ViewSet depending on GET parameters (or how to use search by these complex properties together with simple search from problem 1?).
And I have no understanding if it is possible to provide this kind of search by the same URL as a "simple" search - like site.com/api/people/?city=^New&full_name=John%20Doe (perfectly - with opportunity to document query parameters for OpenAPI schema / Swagger)
So maybe someone knows which is the most elegant way to provide a capability of such complex search with Django/DRF? In which direction should I look?
"full_name" alias needs to be part of your queryset.
You can achieve it by queryset annotation.
In your People view (api/people/ controller) you have to set your queryset to be:
from django.db.models.functions import Concat
from django.db.models import Value
queryset = Human.objects.annotate(fullname=Concat('first_name', Value(' '), 'last_name'))
Also, customize your "filter_backed" to act the way you need.
class PeopleFilterBackend(filters.BaseFilterBackend):
def filter_queryset(self, request, queryset, view):
params_serializer = PeopleFilterSerializer(data=request.params)
params_serializer.is_valid(raise_exception=True)
valid_params = params_serializer.data
if full_name := valid_params.get("full_name")
queryset = queryset.filter(full_name__icountains=full_name)
# insert here all of other filters logic
return queryset
PeopleFilterSerializer is your custom params serializer,
You have to specify there all of your accepted params:
from rest_framework import serializers
class PeopleFilterSerializer(serializers.Serializer):
full_name = serializers.CharField() # set required=False if not required
city = serializer.CharField()
I have a model with two child tables and one parent table. Here is the sample model classes.
# Stores list of unique category names
class Category(models.Model):
category = models.CharField(max_length=20, unique=True, validators=[MinLengthValidator(limit_value=5)])
name = models.CharField(max_length=20, validators=[MinLengthValidator(limit_value=8)])
# Parent class for the next two child classes
class DailyLog(models.Model):
category = models.ForeignKey(Category, on_delete=models.CASCADE)
name = models.CharField(max_length=100, validators=[MinLengthValidator(limit_value=8)])
code = models.CharField(max_length=4, validators=[MinLengthValidator(limit_value=3)])
suggested_values = models.CharField(max_length=100, null=True, blank=True)
# First child class defines display order for dailylog items
class DailyLogDisplayOrder(models.Model):
category_item = models.ForeignKey(DailyLog, on_delete=models.CASCADE)
display_order = models.PositiveIntegerField()
# Second Child class publishes dailylog on a daily bases
class DailyLogCheckList(models.Model):
daily_task = models.ForeignKey(DailyLog, on_delete=models.CASCADE)
publish_date = models.DateField(auto_now=True)
daily_task = DailyTaskCategoryManager() # Log manager to get records per category
How do I perform a cartesian product query? The last column comes from the first child table Dailylogdisplayorder. Here is the raw sql.
select daily_task_id, checklist.publish_date, disporder.display_order
from dailylogchecklist checklist, compliance_dailylogdisplayorder disporder
where checklist.daily_task_id = disporder.category_item_id and checklist.publish_date='2020-07-12'
I have tried using cursor.execute() method per Django documentation. However, I am not able to figure out how to return results in QuyerySet. And also looking for a better way to combine child columns using QuerySet. The return queryset is assigned to a formset.
class DailyTaskCategoryManager(models.Manager):
def with_displayorder(self, user):
from django.db import connection
dtrange = datetime.today().date()
with connection.cursor() as cursor:
cursor.execute("select daily_task_id, checklist.publish_date, disporder.display_order
from dailylogchecklist checklist, compliance_dailylogdisplayorder disporder
where checklist.daily_task_id = disporder.category_item_id and
checklist.publish_date=%s", [dtrange])
result_list = []
for row in cursor.fetchall():
p = self.model(id=row[0], daily_task_id=row[1], publish_date=row[2])
p.display_order = row[3]
result_list.append(p)
return result_list
I already answered to a similar question, You can use prefetch_related() to get the related child table data. Check this answer
https://stackoverflow.com/a/71571509/9561654