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How to create nested serialization from mutliple models uisng django rest framewrok

I am trying to create nested relationship from more than two models in Django Rest Framework.
Thank you in advance for helping me.
I succeed with two models but when I'm trying with three models unable to create nested serialization.
from django.db import models
class Project(models.Model):
project_id = models.AutoField(primary_key=True)
project_name = models.CharField(max_length=255)
def __str__(self):
return self.name
class Site(models.Model):
site_id = models.AutoField(primary_key=True)
site_name = models.CharField(max_length=255)
project_id= models.ForeignKey(Project, related_name="projectid", on_delete=models.CASCADE)
def __str__(self):
return self.site_name
class Aggin(models.Model):
assign_id = models.AutoField(primary_key=True)
site_id = Models.ForeginKey(Site, relate_name="siteid", on_delete=models.CASCADE)
from rest_framework import serializers
from .models import Song, Artist
class ProjectSerializer(serializers.ModelSerializer):
class Meta:
model = Project
fields = ('__all__')
class SiteSerializer(serializers.ModelSerializer):
class Meta:
model = Site
fields = ('__all__')
class AggignSerializer(serializers.ModelSerializer)
class Meta:
model = Aggin
fields = ('__all__')

I think you don't need to primary id field if you wanna use the Django's default foreign key setting. And related_name should be defined from the view of the counterpart model.
from django.db import models
class Project(models.Model):
project_name = models.CharField(max_length=255)
def __str__(self):
return self.name
class Site(models.Model):
site_name = models.CharField(max_length=255)
project = models.ForeignKey(Project, related_name="sites", on_delete=models.CASCADE)
def __str__(self):
return self.site_name
class Aggin(models.Model):
site = Models.ForeginKey(Site, relate_name="assigns", on_delete=models.CASCADE)
And then, in serializer, you can set like the following.
from rest_framework import serializers
from .models import Song, Artist
class ProjectSerializer(serializers.ModelSerializer):
sites = SiteSerializer(read_only = True, many = True)
class Meta:
model = Project
fields = ('id', 'project_name', 'sites')
class SiteSerializer(serializers.ModelSerializer):
assigns = AggignSerializer(read_only = True, many = True)
class Meta:
model = Site
fields = ('id', 'site_name', 'assigns')
class AggignSerializer(serializers.ModelSerializer):
class Meta:
model = Aggin
fields = ('id')

Django - UniqueConstraint not created

I am trying to enforce a constraint for mysql where user is prohibited from inserting twice the same name and model. E.g This should not be allowed to be inserted twice: name:Name1 model:Model1
#Model
class Car(models.Model):
name = models.CharField(max_length=100)
model = models.CharField(max_length=100)
#View
class CarListCreateAPIView(generics.ListCreateAPIView):
serializer_class = CarSerializer
def get_queryset(self):
trip_code = self.kwargs.get("pk")
return Car.objects.filter(trip = trip_code) #Return cars for given trip
#Seializer
class CarSerializer(serializers.ModelSerializer):
class Meta:
model = Car
fields = ('__all__')
constraints = [
models.UniqueConstraint(fields=['name', 'model'], name='car_name_model_constraint')
]
The problem is that the constraint is never created and thus not enforced. What might be the issue with the code?

Use unique_together in class Meta in Model like that:
class Car(models.Model):
name = models.CharField(max_length=100)
model = models.CharField(max_length=100)
class Meta:
unique_together = ['name','model']
More on that here: https://docs.djangoproject.com/en/4.0/ref/models/options/#unique-together

Get objects that are not in manytomany relationship of a different model?

Lets say I have two models and a form:
class Person(models.Model):
first_name = models.CharField(max_length=255)
last_name = models.CharField(max_length=255)
class Car(models.Model):
plate = models.CharField(max_length=255)
persons = models.ManyToManyField(Person)
class CarAddForm(forms.ModelForm):
plate = forms.CharField()
persons = forms.ModelMultipleChoiceField(queryset=Person.objects.all())
class Meta:
model = Car
fields = [
'plate',
'persons'
]
Is there a way to get ModelMultipleChoiceField queryset of people that are NOT associated with any car?
In case of editing Car model object, the queryset should contain people that are NOT associated with any car PLUS people that are associated with the car being edited
PS: maybe there is a better way to achieve this?

You can make use of the limit_choices_to--(Doc) argument of ManyToManyField as
class Car(models.Model):
plate = models.CharField(max_length=255)
persons = models.ManyToManyField(
Person,
limit_choices_to={"car__isnull": True}
)
Alternatively, you can also alter the queryset argument of ModelMultipleChoiceField as
class CarAddForm(forms.ModelForm):
plate = forms.CharField()
persons = forms.ModelMultipleChoiceField(
queryset=Person.objects.filter(car__isnull=True)
)
class Meta:
model = Car
fields = [
'plate',
'persons'
]

You can specify a filter for the query:
from django.db import models
class CarAddForm(forms.ModelForm):
...
persons = forms.ModelMultipleChoiceField(
queryset=Person.objects\
.annotate(car_count=models.Count('cars'))\
.filter(car_count=0))
...
Another options is to override the forms __init__() method. Maybe like this:
from django.db import models
class CarAddForm(forms.ModelForm):
...
def __init__(self, *args, **kwargs):
super().__init__(*args, **kwargs)
self.fields['person'].queryset = self.fields['person'].queryset\
.annotate(car_count=models.Count('cars'))\
.filter(car_count=0))

Django Rest Framework Serializer Doesn't Display ALL Fields

I have a problem where DRF isn't displaying all of my fields correctly for a model class / reference table (specifically the primary key).
My Model Class looks like this (very simple):
class UnitOfIssue(models.Model):
code = models.CharField(max_length=2, primary_key=True)
description = models.CharField(max_length=16)
class Meta:
ordering = ('code',)
def __str__(self):
return "{0} - {1}".format(self.code, self.description)
My Serializer Looks like this:
class UnitOfIssueSerializer(serializers.HyperlinkedModelSerializer):
"""
"""
url = serializers.HyperlinkedIdentityField(
read_only=True,
view_name='unitofissue-detail',
format='html',
lookup_field='code')
class Meta:
model = UnitOfIssue
fields = ('code', 'description', 'url')
# fields = '__all__'
And I'm using a generic view:
class UnitOfIssueDetail(generics.RetrieveUpdateDestroyAPIView):
queryset = UnitOfIssue.objects.all()
serializer_class = UnitOfIssueSerializer
permission_classes = (permissions.IsAuthenticatedOrReadOnly,)
lookup_field = 'code'
In order for the UnitOfIssue primary key code to be displayed in the auto-generated UI, I have to define fields = ('code', 'description', 'url') in the serializer instead of fields = '__all__'.
I want to just be able to use the '__all__' syntax but I can't figure out what's going wrong.
Also, I'm using Django==1.11.13 and djangorestframework==3.8.2

This issue plagued me for weeks, and yet it was such a simple error. I fixed it by changing the serializer base class from:
class UnitOfIssueSerializer(serializers.HyperlinkedModelSerializer):
to:
class UnitOfIssueSerializer(serializers.ModelSerializer):

Lack of data with serialization model with ManyToManyField

Here's are examples I have:
models.py:
class Example(models.Model):
title = models.CharField(...)
description = models.CharField(...)
class Foo(models.Model):
example = models.ManyToManyField(Example)
serializers.py:
class FooSerializer(serializers.ModelSerializer):
class Meta:
model = Foo
fields = '__all__'
depth = 1
views.py:
...
serialized_data = [FooSerializer(foo).data for foo in Foo.objects.all().get]
In output, I receive only Example's IDs, but is there any way I could get title and description fields also (details of m2mfield)? As I understand, Foo.objects.all().get simply doesn't contain this data, but maybe I could somehow get it and use it?
I could also rebuild models if needed, but currently I use m2mf because of needs to contain multiple objects as related to this model data.
update
models.py:
class Event(models.Model):
ts = models.BigIntegerField(editable=False)
class Foo(Event):
user = models.ForeignKey(User, ...)
example = *...(remains to be the same)*
foos = models.ForeignKey('self', **somemore** null=True)
serializers.py:
class EventSerializer(serializers.ModelSerializer):
class Meta:
model = Event
fields = '__all__'
def to_representation(self, instance):
result = {'ts': instance.ts}
if isinstance(instance, Foo):
result['foo'] = FooSerializer(instance).data
return result
class UserSerializer(serializers.ModelSerializer):
class Meta:
model = User
fields = ('id', 'username')
class FooSerializer(serializers.ModelSerializer):
# user = UserSerializer(read_only=True) # with this I have an error: Got AttributeError when attempting to get a value for field 'username' on #serializer 'UserSerializer'
class Meta:
model = Foo
fields = '__all__'
depth = 1

You could use depth attribute to achieve desired output.
The default ModelSerializer uses primary keys for relationships, but
you can also easily generate nested representations using the depth
option.The depth option should be set to an integer value that
indicates the depth of relationships that should be traversed before
reverting to a flat representation.
class FooSerializer(serializers.ModelSerializer):
class Meta:
model = Foo
fields = '__all__'
depth = 1
Apart from the answer, I would like to change your views.py code, cause it seems like very bad :(. Do it on DRF Way as
serialized_data = FooSerializer(Foo.objects.all(), many=True).data<br>
Example View
from rest_framework.viewsets import ModelViewSet
class FooViewset(ModelViewSet):
serializer_class = FooSerializer
queryset = Foo.objects.all()
UPDATE-1
class UserSerializer(serializers.ModelSerializer):
class Meta:
model = User
exclude = ('password',) # add fields that are need to be excluded
class FooSerializer(serializers.ModelSerializer):
user = UserSerializer()
class Meta:
model = Foo
fields = '__all__'
depth = 1
depth = 1 will serializer all fields in the model, (It's same as setting the fields=='__all__' in Meta class of serializer)
UPDATE-2
class FooSerializer(serializers.ModelSerializer):
user = UserSerializer()
class Meta:
model = Foo
fields = '__all__'
depth = 1
def to_representation(self, instance):
real_data = super().to_representation(instance).copy()
# DO YOUR EXTRA CHECKS
child = UserSerializer(instance.child_foo).data
if child:
real_data.update({"child_data": child})
# After your checks, add it to "real_data"
return real_data
and I assumed I have a Foo model as
class Foo(models.Model):
example = models.ManyToManyField(Example)
user = models.ForeignKey(User)
child_foo = models.ForeignKey('self', null=True, blank=True)

In your serializer add depth = 1. Example where 'users' is the related field:
FooSerializer(serializers.ModelSerializer):
class Meta:
model = Foo
fields = ('id', 'account_name', 'users', 'created')
depth = 1