Develop Reference

How can I include in the JSON's GET request the list of foreign keys of a model in Django?

My models have users that can have multiple devices. When I do a GET request on users it returns only the fields specified in the user model, as it should. But I want the option to include in the JSON returned by the GET request the list of devices the user has. How can I do that? Secondly, is there a way I can sometimes get a user with the list of devices in the same JSON, and other times without it? Also, I am really new to Django, and I would appreciate a lot code examples to understand better, if possible.
These are my models:
class User(models.Model):
name = models.CharField(max_length=100)
birth_date = models.DateField()
address = models.CharField(max_length=200)
class Device(models.Model):
description = models.CharField(max_length=200)
location = models.CharField(max_length=200)
max_energy_consumption = models.FloatField()
avg_energy_consuumption = models.FloatField()
user = models.ForeignKey(User, on_delete=models.CASCADE, null=True)
My serializers:
class UserSerializer(serializers.ModelSerializer):
class Meta:
model = User
fields = '__all__'
class DeviceSerializer(serializers.ModelSerializer):
class Meta:
model = Device
fields = '__all__'
And the following default ModelViewSets for CRUD api calls:
class UserViewSet(ModelViewSet):
queryset = User.objects.all()
serializer_class = UserSerializer
class DeviceViewSet(ModelViewSet):
queryset = Device.objects.all()
serializer_class = DeviceSerializer

There are some different ways easiest one would be add a property in your User model and add that to your serializer
class User(models.Model):
name = models.CharField(max_length=100)
birth_date = models.DateField()
address = models.CharField(max_length=200)
#property
def devices(self):
return Device.objects.filter(user_id=self.id).values("location", "description").distinct()
class UserSerializer(serializers.ModelSerializer):
devices = serializers.ReadOnlyField()
class Meta:
model = User
fields = '__all__'
EDIT - for second part of your question:
I have experienced that writing '__all__' in our serializers not the best thing to do when we do not need all the information all the time(performance issues). To address this obsticle making a seperate serializer would be again an easy solution. Whenever I am facing this kind of thing i query same endpoint but send a different qs that i dont use in other endpoint in your case lets say your user viewsets route is something like /api/user/ you can add a qs when you send your get request to your backend and add ?with_devices=true.
Then you can use your second user serializer like this:
class UserViewSet(ModelViewSet):
queryset = User.objects.all()
def get_serializer_class(self):
if self.request.GET.get("with_devices", False):
return UserWithDeviceSerializer
return UserSerializer
where your serializers would be something like:
class UserSerializer(serializers.ModelSerializer):
class Meta:
model = User
fields = ["name", "birth_date", ..so on]
class UserWithDeviceSerializer(serializers.ModelSerializer):
devices = serializers.ReadOnlyField()
class Meta:
model = User
fields = '__all__'
This would give you what you asked in the comment.

AssertionError when calling put or create in Django Rest Framework

I am trying to update my Teachers view in DRF by instead of including the link to the department field, I would display the name of the department. When I added the PrimaryKeyRelated field, I was able to see the department.name but couldnt use update or create within DRF. Is there a way I could change the display without causing the need for the methods or is that not the case?
Error
The `.update()` method does not support writable dotted-source fields by default.
Write an explicit `.update()` method for serializer `school.serializers.TeacherSerializer`, or set `read_only=True` on dotted-source serializer fields.
The `.create()` method does not support writable dotted-source fields by default.
Write an explicit `.create()` method for serializer `school.serializers.TeacherSerializer`, or set `read_only=True` on dotted-source serializer fields.
models.py
class Department(models.Model):
name = models.CharField(max_length=300)
def __str__(self):
return self.name
class Teacher(models.Model):
name = models.CharField(max_length=300)
department = models.ForeignKey(Department, on_delete=models.CASCADE)
tenure = models.BooleanField()
def __str__(self):
return f'{self.name} teaches {self.department}'
# dont need success url if get_absolute_url on create and update view
def get_absolute_url(self):
return reverse('teacher', kwargs={'pk': self.pk})
serializers.py
class TeacherSerializer(serializers.HyperlinkedModelSerializer):
department = serializers.PrimaryKeyRelatedField(
source='department.name', queryset=Department.objects.all())
class Meta:
model = Teacher
fields = ['url', 'name', 'department', 'tenure']
class DepartmentSerializer(serializers.HyperlinkedModelSerializer):
teacher_set = TeacherSerializer(many=True, required=False)
class Meta:
model = Department
fields = ['url', 'name', 'teacher_set']
views.py
class TeacherViewSet(viewsets.ModelViewSet):
queryset = Teacher.objects.all()
serializer_class = TeacherSerializer
permission_classes = [permissions.IsAuthenticatedOrReadOnly]
class DepartmentViewSet(viewsets.ModelViewSet):
queryset = Department.objects.all()
serializer_class = DepartmentSerializer
permission_classes = [permissions.IsAuthenticatedOrReadOnly]

have you tried add related_name for model Teacher in field foreign key and call in serializers? link to docs

Django / DRF - Got AttributeError when attempting to get a value for field `users_answers_set` on serializer `TestTakerSerializer`

everyone. I want to make a test in DRF. But DRF gave me this error:
models.py:
class TestTaker(models.Model):
user = models.ForeignKey(User, on_delete=models.CASCADE)
test = models.ForeignKey(Test, on_delete=models.CASCADE)
class UsersAnswers(models.Model):
test_taker = models.ForeignKey(TestTaker, on_delete=models.CASCADE)
question = models.ForeignKey(Question, on_delete=models.CASCADE)
answer = models.ForeignKey(Answer, on_delete=models.CASCADE)
serializers.py
class UsersAnswersSerializer(serializers.ModelSerializer):
class Meta:
model = UsersAnswers
fields = "__all__"
class TestTakerSerializer(serializers.ModelSerializer):
users_answers_set = UsersAnswersSerializer(many=True)
class Meta:
model = TestTaker
fields = "__all__"
And the error is:
Got AttributeError when attempting to get a value for field `users_answers_set` on serializer `TestTakerSerializer`.
The serializer field might be named incorrectly and not match any attribute or key on the `TestTaker` instance.
Original exception text was: 'TestTaker' object has no attribute 'users_answers_set'.
I tried to add "source" parameter to users_answers_set, but nothing changed.
Thank you.

try usersanswers_set instead of users_answers_set.
or
you can define custom related_name in your model:
class UsersAnswers(models.Model):
test_taker = models.ForeignKey(TestTaker, related_name="users_answers_set" , on_delete=models.CASCADE)

Django rest framework AttributeError after GET request

During a GET request, Django give me this error:
Got AttributeError when attempting to get a value for field `name` on serializer `projectSerializer`.
The serializer field might be named incorrectly and not match any attribute or key on the `ProjectTask` instance.
Original exception text was: 'ProjectTask' object has no attribute 'name'.
I'm pretty new to django and rest_framework, here's the code:
models.py
class Project(models.Model):
name = models.CharField(max_length=50)
class ProjectTask(models.Model):
project = models.ForeignKey(Project,on_delete=models.CASCADE)
description = models.CharField(max_length=200)
status = models.IntegerField()
serializers.py
class projectTaskSerializer(serializers.ModelSerializer):
class Meta:
model = ProjectTask
fields = ['description','status']
class projectSerializer(serializers.ModelSerializer):
tasks = projectTaskSerializer(many=True)
class Meta:
model = Project
fields = ['name','tasks']
views.py (I'm only mentioning the get function that is being called to avoid cluttering the question
def get(self, request):
projects = ProjectTask.objects.all()
serialized_projects = projectSerializer(projects,many = True)
return Response({'projects' : serialized_projects.data})

How can I create form using this django model?

I am trying to create form using this model. I want to add data in this database model using form to perform CRUD operation. I am using MySQL database.
models.py
from django.db import models
from .managers import CategoryManager, SubCategoryManager
# this is my parent model
class Node(models.Model):
name = models.CharField(max_length=150)
parent = models.ForeignKey(
'self',
on_delete=models.CASCADE,
related_name='children',
null=True,
blank=True
)
def __str__(self):
return self.name
class Meta:
ordering = ('name',)
verbose_name_plural = 'Nodes'
class Category(Node):
object = CategoryManager()
class Meta:
proxy = True
verbose_name_plural = 'Categories'
class SubCategory(Node):
object = SubCategoryManager()
class Meta:
proxy = True
verbose_name_plural = 'SubCategories'
class Product(models.Model):
sub_category = models.ForeignKey(
SubCategory, on_delete=models.CASCADE
)
name = models.CharField(max_length=100)
description = models.TextField(blank=True)
def __str__(self):
return self.name

Try the Imagine smart compiler which allows automatic generating of code + tests for your CRUD APIs and Django models from a very simple config. Amongst other things, it generates code in the correct way to handle foreign key relationships in Django Views. You can also try a demo here imagine.ai/demo
PS: Something like this simple config will generate all the code for the CRUD API along with the tests!
Model Node {
id integer [primary-key]
name string [max-length 150]
}
Model Product {
id integer [primary-key]
name string [max-length 100]
description string [nullable]
}